GROWTH OF EGGS AND EGG-STRlNGS IN NEPHELIS. 207 



7 mm.), and have lost the club-shape seen in fig. 6. The 

 follicles towards either extremity have become larger, and 

 the string has in consequence assumed a nearly uniform 

 width for the greater part of its length. It is during this 

 season that we meet with strings which are in process of 

 dissolving, and among the loosened elements of such strings 

 are always found spermatozoa. It has occurred to me that 

 possibly such appearances may have led Robin to the theory 

 of "ovo-spermatophores.'"' 



A tolerably distinct membrane appears to envelope the 

 ovum very soon after the cell-outline is seen. I have repre- 

 sented this membrane with double outline in fig. 13, but 

 I am disposed to admit that I have somewhat exaggerated 

 this point. The drawing conveys, however, a sufficiently 

 accurate notion of the appearance of the membrane. The 

 membrane evidently arises from the protoplasm ; but whether 

 from the enclosed cell-body or from the enveloping proto- 

 plasm of the follicle, I am not able to say. 



With the growth of the ovum the germinal vesicle in- 

 creases in size, but not in the same proportion as the ovum. 

 From the following measurements it will be seen that, Avhile 

 the diameter of the egg has increased about elevenfold, that 

 of the germinal vesicle has only quadrupled. 



Ovum. Germ, vesicle. 

 •015 mm. '01 mm. 



•062 „ -02 „ 



•095 „ •OS „ 



•17 „ -04 „ 



The Yolk Nucleus. — In eggs that have attained the size of 

 about 1 mm. I have frequently found one or more corpuscles 

 embedded in the vitellus, usually near the periphery. In a 

 fresh -laid egg I once counted as many as fifteen of these 

 bodies. They vary considerably from a spherical form, are 

 quite refractive, and present a granular appearance. They 

 differ also much in size, the largest observed measuring 

 '016 mm. Their variable number and total absence in some 

 eggs show that they have no special morphological value. 



I am inclined to think that they are analogous to the 

 yolk nucleus (" Dotterkern") found in the Amphibian egg. 

 O. Hertwig (No. 8, p. 37) is of the opinion that this body 

 is simply a peculiar aggregation of food stuff, and proposes 

 to call it " Dotterconcrement.'^ 



It will be seen from the foregoing that the origin of the 

 egg inNephelis differs somewhat from the same in Piscicola, 

 as described by Ludwig (No. 15, p. 63-67). It may be well 

 here to recapitulate briefly my observations on this subject, 



