568 EMBEYOLOGY OF THE LOWER VERTEBRATES ch. 



end of a glass siphon drawn out to a fine point so as to produce the 

 effect of a shower of rain. Within a week or two breeding took place. 

 The chief difficulty in the way of cutting sections of Frog's eggs 

 is due to the presence of the jelly-like envelope. This may be got rid 

 of by prolonged soaking, six months or more, in -5% formalin 

 (Ogushi, 1908), or by fixing in Zenker's fluid and leaving the eggs in 

 this fluid renewing it after 2 to 3 days and continuing the treatment 



Fig. 253. — Stages in the development of JPhyllomedusa hypodhondrialis. 

 E, eye ; e.g, exterpal gill ; op, operculum ; ot, otocyst. 



for 8 to 14 days or longer, shaking gently so as to remove the envelopes 

 (Kallius, 1908). 



For cutting sections paraffin is commonly used but it should be 

 supplemented by celloidin e.g. the clove-oil method mentioned under 

 Amphioxus. 



In the Urodeles the eggs are commonly laid singly in water and 

 attached to water plants (Triton) or other solid objects such as logs 

 or stones {Proteus, Necturus). In Cryptobranchus and Ampliiuma 

 they form a beaded string, adjacent envelopes being connected 

 together by a narrow isthmus. 



Fertilization is rarely external (Cryptobranchus — Smith, 1912). 

 In the Newts the female takes up a spermatophore into the cloaca. 



