I So MUNSON. [Vol. XV. 



recent years. The theory of Waldeyer also offered in explana- 

 tion of two zones in the cytoplasm of the bird's egg, and 

 extended also to the observation of Pfliiger in the egg of the 

 cat, namely, the direct apposition to the primitive egg cell of 

 the outer zone, conceived to be derived from the follicle epi- 

 thelium, does not apply in the present case, inasmuch as no 

 true follicle epithelium can be said to be present. Equally 

 inapplicable is the somewhat vague but decidedly radical 

 theory advanced by Leuckart ('53) in regard to all eggs, and 

 the somewhat similar though more metaphysical theory 

 advanced by Balbiani ('83), according to which, in myriapods, 

 the egg consists of a " partie germinative fondamental " 

 and of a " partie nutritive," each of these parts being consti- 

 tuted " isolement et pour son propre compte." The objection 

 to such an explanation would be that in the egg of Limulus the 

 division of the cytoplasm into an outer and inner more or less 

 granular zone is not a constant, but a periodical feature. 



It remains to be considered how far the direct elimination of 

 chromatin from the germinal vesicle into the surrounding cyto- 

 plasm can explain the existence of the internal granular zone. 

 Such an explanation has been offered by Will in eggs of 

 amphibians and insects, by Bambeke ('93) and by Calkins ('95) 

 in the egg of Lumbricus. Calkins's observations receive in- 

 creased interest and importance from the evident acceptance 

 of his results by Professor Wilson ('96) in his new work on 

 the cell, and the evident stress which the latter author places 

 upon it in his theory of synthetic metabolism of the chromatin 

 of the germinal vesicle. In addition to the doubt cast upon Cal- 

 kins's results by the observations of Miss Foot ('96) on the 

 eggs of a closely allied species, Allolobophora, from which she 

 seems inclined to believe that Calkins's results were obtained 

 from pathological material, the following considerations may 

 be urged against the sufficiency of the theory of elimination 

 of chromatin to explain the internal deeply staining zone : 

 I . It does not explain the existence of the hyaline zone, which 

 appears to precede or to follow the granular condition. The 

 existence of the hyaline zone proves that the zone is not due 

 to the extruded chromatin granules. 2. The elimination of 



