ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 545 



respomliug branchial lobes posteriorly. lu front of, and between, 

 the anterior lobes is an air-bubble supposed to be res2)iratory in func- 

 tion. By the 3rd day the four lobes have increased and coalesced to 

 form a " racket-shaped figure." During the 4th and 5th days the 

 cranium and sense organs (excepting the eye) are developed, the 

 olfactory organs aj)pearing much later than in other Anura. The 

 branchiae apj)ear as digitiform processes of the lateral masses. By 

 the 6th day they are six in number on the right side and seven on the 

 left. By the 7th day there are ten for each side. In addition there 

 are tentacular ramifications which coil about beneath the walls of the 

 ovum. M. Heron-Royer compares these (provisional) organs with 

 the arborescent vascular jjrocesses described by M. Bavay in the 

 developing ovum of Hylocles Martinicencis, and justly explains 

 their origin by reference to the terrestrial conditions of the deve- 

 lopment of the young Alytes. 



The heart, first observed on the 6th day, is covered merely by a 

 pericardium, and not by the vitelline sac, as in other Anura. On 

 the 8th day appears the abdominal investment, inclosing a portion 

 of the disappearing vitellus, and distinguished therefrom by pigmenta- 

 tion. By the 9th day the yellow-coloured intestine is completely 

 formed, and the vitellus absorbed. The eye is completed on the 

 13th day, when the choroidal fissure disajjpears, and the iris, 

 hitherto white, finally assumes its metallic yellow colour. 



On the 14th day the external branchiae disappear, the right oper- 

 culum being the last structure to be formed. The natatory mem- 

 branes now develope, the caudal appendage elongates, and the embryo 

 is ready to escape from the egg. 



There are three investments to the egg : (1) an " external en- 

 velope," inclosing an albuminous layer ; (2) an " inner capsule," oval 

 in shape; and ;3) the "chorion," directly investing the ovum j^-oper, 

 which is spherical. 



M. Heron-Royer disagrees entirely with the previous observations 

 on the mode of the escape of the embryo from the egg. He finds 

 that the young Alytes does not (as de L'Isle and others had asserted) 

 simply split the envelopes of the ovum, like a bean-pod ; but rather 

 that the exit of the embryo is at first conditioned by moisture. 

 Exposed to moist conditions, the albuminous layer beneath the " ex- 

 ternal envelope " absorbs moisture and expands its investment. The 

 " inner capsule " in the presence of the moisture becomes more sujiple 

 aud allows greater freedom of movement to the embryo, which now 

 employs the external comb-like lamella? on its jaws to effect an open- 

 ing, first in the chorion, then in the ' inner capsule,' and finally in 

 the " external envelope." Finally, bending its body into a bow, aud 

 fixing its tail against tlie capsule, the embryo, by a final ofibrt, forces 

 its way from the egg " comme un projectile." Sometimes tlic young 

 Alyfes sticks half-way or endeavours to emerge tail first, usually with 

 fatal cfjnsoquences. 



M. Heron-Royer, by applying abnormal warmth and moisture, 

 brought abuut the development of Alytes within 15 days. In normal 

 circumstances, however, 24 days intervene between fecundation of 



