196 ON SEXUAL REPRODUCTION IN THE INFUSORIA. 



Each is a homogeneous, transparent, spherical vesicle, at first 

 quite free from granulations, and having a diameter of not 

 more than '007 mm. 



These four corpuscles are the rudiments of the eggs, 

 destined ere long to undergo fertilization. And there can 

 be little doubt that, notwithstanding their apparent diver- 

 sity of position in different specimens, they are enclosed 

 within one end of the same delicate membranous tube which 

 contains the other more numerous ovarian fragments. For, 

 when examined at maturity, with the aid of reagents, a faint 

 line may be detected in the intervals between the eggs, pass- 

 ing into the clear border on either side of each. 



In spite of their minute size, M. Balbiani succeeded in 

 extracting uninjured some of the young eggs from the 

 parent -body, and subjecting them to the action of the sur- 

 rounding w^ater. Thereupon each egg resolved itself into 

 two hollow membranous spheres, the smaller being enclosed 

 within the other, and separated from it by a considerable in- 

 terval. Other reagents, such as acetic acid or iodine, pro- 

 duced the same result more rapidly. These (of course much 

 diluted), could even be applied to the egg while yet within 

 the body of the animal, provided the movements of the latter 

 were first restrained by means of a little gentle compression. 



Of the two spheres, the outer would seem to represent a 

 vitelline membrane ; the inner a germinal vesicle. A few 

 free granules may sometimes be seen within the latter ; but, 

 as yet, no other egg contents are to be observed. The evolu- 

 tion of one egg always keeps pace with that of its fellows, 

 no one of the four being in a more advanced stage of deve- 

 lopment than the others. 



(To be vontinued.) 



