Trypanosoma Ziemanni, from the blood of the little owl. The stages shown in Figs. 52–54 are passed inside the gnat. The spiral and pear-shaped bodies of Fig. 54 pass from the gnat’s proboscis into the blood of the little owl, and grow there into the large forms here figured. A, B, and C are females, destined to be fertilized by spermatozoa when swallowed by a gnat. D and E are male Trypanosomes, which will give rise each to eight fertilizing individuals or spermatozoa as shown in Fig. 56—when swallowed by a gnat.
Trypanosoma Ziemanni, from the gut of the gnat
The Freshwater Jelly-fish of Regent’s Park (Limnocodium Sowerbii)
It was discovered in the tropical lily tank of the Botanical Gardens in June, 1880, and swarmed in great numbers year after year—then suddenly disappeared. It has since been found in similar tanks in Sheffield, Lyons, and Munich. Only male specimens were discovered, and the native home of the wonderful visitor is still unknown.
The Freshwater Jelly-fish of Lake Tanganyika (Limnocnida Tanganyicae), Since its discovery in Tanganyika it has been found also in the Lake Victoria Nyanza and in pools in the Upper Niger basin.
Drawings by Professor Grassi, of Rome, of the young of the common Eel and its metamorphosis. All of the natural size. The uppermost figure represents a transparent glass-like creature—which was known as a rare “find” to marine naturalists, and received the name Leptocephalus. Really it lives in vast numbers in great depths of the sea—five hundred fathoms and more. It is hatched here from the eggs of the common Eel which descends from the ponds, lakes, and rivers of Europe in order to breed in these great depths. The gradual change of the Leptocephalus into a young Eel or “Elver” is shown, and was discovered by Grassi. The young Eels leave the great depth of the ocean and ascend the rivers in immense shoals of many hundred thousand individuals, and wriggle their way up banks and rocks into the small streams and pools of the continent.
The unicellular parasite Benedenia, from the gut of the common Poulp or Octopus. 1 is the normal male individual; 2 and 3 show stages in the production of spermatozoa on its surface by budding; 4, 5 and 6 show a female parasite with spermatozoa approaching it.
Drawing of the skull and lower jaw of the Meritherium, discovered by Dr. Andrews in the Upper Eocene of the Fayum Desert. The shape of the skull and proportions of face and jaw are like those of an ordinary hoofed mammal such as the pig; but the cheek-teeth are similar to those of the Mastodon, and whilst the full complement of teeth is present in the front of the upper jaw, we can distinguish the big tusk-like incisor which alone survives on each side in Palæomastodon, Mastodon, and the elephants, as the great pair of tusks.
Diagrammatic representation of the structures present in a typical cell (after Wilson). Note the two centrosomes, sometimes single.
(a) Cell of the asexual generation of the cryptogam Pellia epiphylla: the nucleus is about to divide, a polar ray-formation is present at each end of the spindle-shaped nucleus, the chromosomes have divided into two horizontal groups each of sixteen pieces: sixteen is the number of the chromosomes of the ordinary tissue cells of Pellia. (b) Cell of the sexual generation of the same plant (Pellia) in the same phase of division, but with the reduced number of chromosomes—namely, eight in each half of the dividing nucleus. The completed cells of the sexual generation have only eight chromosomes. (c) Somatic or tissue cell of Salamander showing twenty-four ∨-shaped chromosomes, each of which is becoming longitudinally split as a preliminary to division. (d) Sperm-mother-cell from testis of Salamander, showing the reduced number of chromosomes of the sexual cells—namely, twelve; each is split longitudinally. (From original drawings by Prof. Farmer and Mr. Moore.)
A diagram showing the life-history and migration of the Malaria parasite, Laverania Malariæ, as discovered by Laveran, Ross, and Grassi. The stages above the dotted line take place in the blood of man. The oblong-pointed parasite is seen entering the blood at n just below No. 1. The circles represent the red blood-discs of man. Schizogony means multiplication by simple division or splitting, and it is seen in Nos. 6, 7, 8, 9, and 10. The stages below the dotted line are passed in the body of the spot-winged gnats of the genus Anopheles. A peculiar crescent or sausage-shaped condition is assumed by the parasite inside the red corpuscle No. VI. These are found to be of two kinds, male and female, Nos. VIIa and VIIb. They are swallowed by the spot-winged gnat when it sucks the blood of an infected man. Here in the gut of the gnat they become spherical; the male spheres produce spermatozoa No. Xa, which fuse with and fertilize the female spheres or egg-cells No. XI. An active worm-like form No. XIII results, which pushes its way partly through the wall of the gnat’s gut, and is then nourished by the gnat’s blood. It swells up, divides internally again and again, and is enclosed in a firm transparent case or cyst, Nos. XIV to XVIII. The cysts are far larger in proportion than is shown in the diagram, and are visible to the naked eye. The final product of the breaking up, which is called sporogony, is a vast number of needle-shaped spores or young (called Exotospores, as opposed to the Enhæmospores, which are formed in the human blood, as seen in Nos. 9 and 10, and serve there to spread the infection among the red corpuscles). The needle-shaped spores formed in the gnat’s body accumulate in its salivary glands, and pass out by the mouth of the gnat when it stabs a new human victim who thus becomes infected, No. XIX.
Various species of Trypanosoma from the blood of mammals, birds, and reptiles. A. T. Lewisii, from the blood of rats; B. T. Brucei, the parasite of the Nagana or Tsetze-fly disease, found in the blood of horses, cattle, and big game; C. T. gambiense, the parasite causing Sleeping Sickness in man; D. T. equinum, which causes the mal de caderas in South American horse ranches; E. T. noctuæ, from the blood of the little owl, Athene noctua; F. T. avium, found in the blood of many birds; G. a species found in the blood of Indian pigeons; H. T. ziemanni, a second species from the blood of the little owl; J. T. damoniæ, from the blood of a tortoise; c.g., granules; v., vacuole; l.s., fold of the crest or undulating membrane.
The earliest discovered Trypanosome, described by Gruby in 1843 as “Trypanosoma sanguinis” and found by him in the blood of the common esculent Frog.
It was not noticed again until it was re-discovered by Lankester in 1871, who published the figure of it in the Quarterly Journal of Microscopical Science in that year.
The amœba is one of the simplest of all animals, and gives us a hint of the original ancestors. It looks like a tiny irregular speck of greyish jelly, about 1/100th of an inch in diameter. It is commonly found gliding on the mud or weeds in ponds, where it engulfs its microscopic food by means of out-flowing lobes (PS). The food vacuole (FV) contains ingested food. From the contractile vacuole (CV) the waste matter is discharged. N is the nucleus, GR, granules.
The Volvox is found in some canals and the like. It is one of the first animals to suggest the beginning of a body. It is a colony of a thousand or even ten thousand cells, but they are all cells of one kind. In multicellular animals the cells are of different kinds with different functions. Each of the ordinary cells (marked 5) has two lashes or flagella. Daughter colonies inside the Parent colony are being formed at 3, 4, and 2. The development of germ-cells is shown at 1.
One of the simplest multicellular animals, illustrating the beginning of a body. There is a setting apart of egg-cells and sperm-cells, distinct from body-cells; the collared lashed cells on the margin are different in kind from those farther in. Thus, as in indubitable multicellular animals, division of labour has begun