in 



AMPHIBIA. 



AMPHIBIA. 



178 



and toward* the head mudl furrow is men which separates the heed 

 from the abdomen, and the rudiment* of a ipine are distinctly vixiUo 

 along iU ooorex border. 



By the 2nd of My the position of the embryo u changed, and the 

 tail has already amumed it* oar-like form. The embryo begin* to 

 more, and it* heart may be Men to beat ; colour, too, begin* to be 

 Mi-went This appear* to be a critical itate of the embryo; for almost 

 half of those of which the development wa* watched by Rusooni, died 

 at thi* period or aoon after. 3rd May. On one ride of the bead, and 

 be/or* the two elevation* which are the rudiment* of the fore-feet, 

 filament* to the number of four on each aide may be observed. 4th 

 Hay. The change* of position become frequent. In that here presented 

 the embryo shows the lower part of iU head and trunk, which is white 

 inclining to green. On the chest between the gills of the two sides, 

 where the pulsation* of the heart are seen, small irregular blackish 

 spot* are observable. Before the two claapers are seen aUto other 

 blackish spots, forming the junction of the two bandit which run along 

 the back, a* shown in the preceding figure. The circulation of the 

 blood, which is simple, and performed by a single curved vessel, ia 

 seen in the gill*, which are of a glassy transparence, and consist only 

 of a single filament without leaflets a* yet 5th May. Traces of the 

 eyes may now be just seen ; and the rudiment* of the two leaflet* are 

 perceptible on the two longest gills. 6th Hay. The upper small figure 

 shows the young Salamander, seen from above, and of the natural size, 

 just escaped from the envelope. Before it* escape, the embryo a* it 

 enlarge* gradually dilate* the envelope, which at last it tears, and so 

 force* its way out. As yet the eye* are scarcely defined, though they 

 form two prominence* on the sides of the head, and it* mouth is so 

 slightly traced that attentive observation is required to detect it ; for 

 it is indicated only by a slight transverse depression beneath the head, 

 and between the two prominences formed by the eye*, and in the 

 middle of the space between the anterior border of the head and the 

 origin of the neck. Its fore-feet begin to separate like buds from the 

 gills, which last are gradually furnished with small leaflets. 



May C. 



Stagei of dcrelopmcnt of Triton criitatiu after exclusion from the egg. 



a shows the Salamander in thin stage, magnified and seen from 

 In-low ; bb are the two prominences formed by the globes of the eyes, 

 and between them is the slight depression which afterwards becomes 

 the mouth ; c, the hook of the right side ; d, the gills of the same 

 side ; , rudiment of fore-feet of the same side ; / represents the same 

 seen in profile, and <j the same *een from above. 



Further stages of development of Triton crulatu*. 



The middle and small figure alnv shews the natural size f tlic 

 Salamander-Tadpole on the 18th of Hay, twelve days afttr its exclusion 

 fp 'in the egg. By this time tin- furo-feet have become lengthened, and 

 vided at their extremity like a bicuspid tooth; these two 

 tubercle* elongate, and are converted into two toe*. Now the eye* 

 are disclosed ; the pupil black, the white speckled with various colours. 

 The yellow back of the little animal lias become green, and the gills 

 are now furnished with leaflet*, in which red blood circulate*. The 

 transverse depression between the eyes above noticed has become a 



very large mouth, whose extremities extend on the side* of the head 

 to the eyes. The head, hitherto narrow behind, ha* become nm.li 

 enlarged near the origin of the gill*. The two hooks by which the 

 animal anchored itself have disappeared, and the opaque body has 

 become so transparent that the action of the heart and the form an. I 

 di*position of the abdominal viscera may be observed in the living 

 animal With thi* advance in organisation the sluggishness of the 

 animal has vanished, and its habit* are now manifested. It may be 

 seen near the surface, hiding beneath leaves or swimming with 

 rapidity. If, while it floats at rest, a small aquatic insect should pas* 

 1-i-f'nv it near the surface, it pursue* it deliberately, and as soon as it 

 approaches within reach, darts upon it and swallows the prey. Here 

 then we have the little Salamander in the enjoyment of active 

 animal life. 



Jul) IS. 



Further stages of development of Triton crutatut. 



a, nhovB the young Salamander at this stage, natural size, << n from above ; 

 and *, the same magnified, seen from above and in profile. 



Hy the 28th of May the Salamander has put on the form above 

 given in the upper figures, seen from above. About this time the 

 hind-feet begin to appear, and the fore-feet are we'll di-vi-loju-d ; these 

 last are, as will be seen, long in proportion to the trunk. Tho 

 following are the principal points manifested under the microscope in 

 this stage : 1, two small fmiin-nues or excrescences, extending from 

 the axilla! to the abdomen ; 2, the pariotes of the abdomen take the 

 colour of the insects on which the animal feeds ; 3, the changes of 

 colour from yellow to green, during the growth of the tadpole, are 

 purely accidental, aud commence immediately on the escape of the 

 animal from the egg ; 4, the inner toes first push forth, and this holds 

 good also with regard to the hind-feet ; 5, the amylaceous bone of tin- 

 organ of hearing is now fonm-d, and may be seen through the skull 



and skin ; 6, at this 

 period, and even sooner, 

 the animal begins to 

 expel air from the 

 mouth. The two lower 

 cuts show the same 

 salamander on the 

 1'Jth .Inn-. : the xuiall 

 figure represents it of 

 the natural size and aa 

 seen from above, and 

 tin- larger figure man- 

 iiilii-.l and in ]>i 

 Now the hind -in t ha\e 

 almost attained th.-ir 



JT~ development, though 



tin- til'tli t..,- in wanting. 



Last itage of the tadpole of Triton cf Matin. The lungs extend about 

 half-way down thu trunk, im.l arc visible through tin- ]Mirii-t.<-i of tin- 

 abdomen. The longest gills, which were furni.-lic.l with only 13 or 

 14 leafletH 13 or 14 day . have now nearly 20. 



On the 1 8th of July the young Salamander, as represented aWc. 

 had arrived at the maturity of ite tadpole state, and it is reprc- 

 watching a small mollusk to ascertain whether it is living and fit tor 

 prey. Ruscoiii found that on this day tin- ^ilUajipearcd rather shorter 

 than on the day before. On the next day the leaflets at the extremities 

 of the gills were obliterated, and the gill-stem itself was shortened. 

 Un the 27th of July the Salamander had lost even the smallest trace 



