CHAPTER VI I. 

 AMPHIBIA'. 



The eggs of most Ampiiibia^ are laid in water. They are smallish 

 nearly spherical bodies, and in the majority of known Anura (all the 

 European species), and in many XJrodela (Amblystoma, Axolotl, 

 though not in the common Newt) part of the surface is dark or 

 black, owing to the presence of a superficial layer of pigment, while 

 the remainder is nnj igmented. The pigmented part is at the upper 

 pole of the egg, and contains the germinal vesicle till the time of its 

 atrophy; and the yolk-granules in it are smaller than those in the un- 

 pigmented part. The ovum is closely surrounded by a vitelline mem- 

 brane'', and receives, in its passage down the oviduct, a gelatinous 

 investment of varying structure. 



In the Anura the eggs are fertilized as they leave the oviduct. 

 In some of the Urodela the mode of fertilization is still imperfectly 

 understood. In Salamanders and probably Newts it is ioternal*; 



^ The following classification of the Amphibia is employed in the present chapter : 

 J . { Aglossa. 



• ■^•1111^8'. (Phaneroglossa. 



fn \ Trachystomata. 



PeRENNIBRANCHIATA vr, , -'i 



IProteidae. 

 TT TT J 1 in iAmvihiumidas. 



II. Urodela. ^. Cabucibranchiata JMenopomida.. 



n^ \ Amblystomidffi. 



Myctodeba ' q , ■' J ■ ^ 



( oalamandridaB. 



III. Gymnophiona . 



2 I am under great obligations to Mr Parker for having kindly supplied me, in 

 answer to my questions, with a large amount of valuable information on the develop- 

 ment of the Amphibia. 



3 Within the vitelline membrane there appears to be present, in the Anura at any 

 rate, a very delicate membrane closely applied to the yolk. 



* Allen Thomson informs me that he has watched the process of fertilization in 

 the Kewt, and that the male deposits the semen in the water close to the female. 

 From the water it seems to enter the female generative aperture. Von Siebold has 

 shewn that there is present in female Newts and Salamanders a spermatic bursa. In 

 this bursa the spermatozoa long (three months) retain their vitality in some Sala- 

 manders. Various peculiarities in the gestation are to be explained by this fact. 



