3IO JORDAN. [Vol. VIII. 



sion. There is good reason to think, then, that during the 

 process of oviposition (see p. 277) the Qgg passes from the 

 oviduct into the cloaca, where it is fertihzed by sperma- 

 tozoa pressed out of the receptacle, and thence is extruded 

 along with a quantity of gelatinous secretion that glues 

 together the leaves of the "nest." All of these actions are 

 undoubtedly to a certain degree coordinated under voluntary 

 control. The occasional fertilization of one of the excreted 

 eggs is probably due to the chance presence of a stray sperma- 

 tozoon in the cloaca. 



Since it is true, then, that the fertilization of the Qg% does 

 not take place until the o^gg reaches the cloaca, the spermatozoa 

 which strive for entrance there find themselves confronted with 

 a formidable egg-membrane. The consistency of this membrane 

 can be adequately realized only through repeated attempts to 

 remove it from the living Qgg. So improbable did it appear to 

 me that spermatozoa should be able to pierce this dense and 

 leathery covering, that I sought long and carefully for a 

 micropylar opening. The search, however, was fruitless, and 

 this negative result, together with the fact that spermatozoa 

 •ordinarily penetrate the egg at different and widely separated 

 points, oblige me to admit, though somewhat reluctantly, the 

 probability that spermatozoa somehow succeed in making their 

 way through the membrane. 



The points of entrance of the spermatozoa may be seen 

 as slightly depressed, pigmented areas on the surface of 

 the living Qg^ freed from its membrane, one to two hours 

 after oviposition (Fig. 6). There are several of these points, 

 as a rule, indicating the penetration of several spermatozoa, 

 an inference which, as we shall see, is fully sustained by 

 the evidence from sections. There is no fixed and predeter- 

 mined point of entrance ; the spermatozoa may invade the &gg 

 in the neighborhood of the "light spot" (Fig. 6), or they may 

 force an entrance near the equator of the egg. Most fre- 

 quently they enter the upper (pigmented) pole, but I have 

 several times observed them entering the lower hemisphere. 

 Roux ('87, p. 174) has established a similar indeterminateness 

 in the point of penetration of the spermatozoa of Rana. 



