SPERMA-EGGS 53 



fecundation of the female without actual copulation. The female 

 takes up such a eleposited spermatophore with the cloacal lips, 

 squeezes the sperma out of the capsule which remains behind, and 

 either conveys the former into a special receptaculum seminis, 

 e.g. in Salamandra afra and in Triton, or the spermatozoa wriggle 

 their way, thanks to the undulating tail, directly up the oviducts 

 to the ova. 



The spermatophores are composed of a colourless, soft, gela- 

 tinous mass, which is probably produced by the cloacal gland. 

 The shell of jelly is in fact a cast of the cloacal 

 cavity, reproducing all its ridges, furrows and 

 folds, while a toad -stool -shaped papilla of 

 the cloaca makes the inside lumen of the cast, 

 e.g. in Triton. Those of Salamandra maculosa 

 are much simpler, consisting, in conformity 

 with the absence of a cloacal papilla, merely of 

 a cone with a globular mass of sperma on the ^^^^ ^ _^ bell-shaped 

 top. Those of Amhly stoma are similar. spermatophore of 



The spermatozoa of the Anura show con- fl^^^iZf^' 

 siderable differences in the various genera, of 

 which, however, only the European forms have been properly 

 examined. The " head " is wound like a corkscrew in Discoglossus, 

 Pelohates, and Pelodytes ; spindle-shaped, more or less curved, in 

 Rana temporaria and R. agilis, Hyla, Biifo and Bombinator, in 

 the latter with an irregular membrane on one side ; cylindrical 

 in Rana esculenta and R. arvalis. The tail is mostly long and 

 filiform, but in Bufo vulgaris and Discoglossus it is provided with 

 an undulating membrane. Their size is generally very small, 

 only about O'l mm., excepting those of Discoglossus which reach 

 the astonishing length of 3 mm. These differences in shape, 

 especially that of the head, explain why species of the same 

 genus, e.g. Rana temporaria and R. arvalis, cannot fertilise each 

 other. 



The eggs differ much in size, colour, and numbers. They 

 are holoblastic, with unequal cleavage, but those species which 

 possess an unusual amount of food-yolk, for instance RhacopJwriis 

 schlegeli and the Apoda, approach the meroblastic type of segmen- 

 tation. As a rule, the greater the amount of yolk, the smaller 

 is the number of eggs .produced. But the number which is laid 



1 Zeitsclir. wiss. Zool. xlix. 1889, p. 583. 



