MUSEUM OF COMPARATIVE ZOOLOGY. 105 



radiata." The apparatus has the form of a crater-like depression, about 

 as described by Buchholz and Ransom. Where the membranes take the 

 direction of the crater, they form folds with the pointed ends directed 

 inward. But of more interest are his statements, that the zona radiata 

 externa takes the greater share in the formation of the crater, and that 

 "other tissues, especially the endothelium and granulosa cells, participate in 

 the same." Owsjannikow was thus, I believe, the first person after W. 

 Miiller ('75) to call attention to an intimate relation between granulosa 

 and micropyle. 1 But there are some elements of uncertainty about his 

 descriptions and figures that seem to baffle every attempt to reduce 

 them to harmony. The most perplexing thing about his description is 

 the use of the term " endothelium," which is at first used for Osmerus 

 in the following connection (p. 10): "Die Graafschen Follikel der 

 Osmeruseier bestehen aus Endothel, Gefassen, Bindegewebe und Folli- 

 kelzellen." In the description of other eggs (Perca) the word " Endo- 

 thel " is also used as though applied to cells which lie outside the 

 vascular layer, and even as though including the germinal epithelium 

 of other authors (p. 4). Unless an endothelium having a very different 

 position from that previously described by him is meant, when he 

 says that it participates (as well as the granulosa) in the micropylar 

 structure, I believe that the author has fallen into some error ; for I 

 am of opinion that neither the connective-tissue layer with its blood- 

 vessels nor the germinal epithelium shares directly in the formation of 

 the micropylar apparatus. Neither do I believe that there exists inside 

 the connective tissue any layer of cells except the granulosa. Moreover, 

 I do not think that any layer of endothelium, either inside or outside 

 the vascular layer, has been figured as sharing in the formation of the 

 micropyle. It does not help matters in the least to add that the author 

 discountenances (p. 4) any attempt to draw a distinction between epi- 

 thelium and endothelium ; for after saying that " Endothel und Granu- 

 losazellen " share in this formation, he proceeds with a description 

 which certainly allows the assumption that there is only a single layer 

 of cells involved, to which, however, he gives successively the names of 

 granulosa, endothelium, and epithelium. 



1 Although published several years ago, Owsjannikow's studies were not made 

 until some time after I had demonstrated tlie conditions in Lepidosteus which have 

 been described above. His paper, as well as the more recent one of Cunningham, 

 has therefore had no influence in determining the course or the results of my studies 

 on Lepidosteus, nor did it influence me to suggest a comparative study on the eggs 

 of bony fishes, such as Mr. Eigenmann has undertaken ; for I had already proposed 

 that question to one of my students before either paper was published. 



