MUSEUM OF COMPARATIVE ZOOLOGY. 119 



Postscript. 



Since the completion of the present paper, I have received from the 

 author, Dr. J. Beard, a copy of his "Preliminary Notice, — On the 

 Early Development of Lejndosteus osseus." This paper was presented to 

 the Eoyal Society of London, April 20, 1889, and was printed in the 

 Proceedings of the Society, Vol. XLVI. pp. 108-118, May 16, 1889. 



Dr. Beard's material was procured by him in the spring of 1888 from 

 the same place as that which supplied Mr. Agassiz and myself, — Black 

 Lake, New York. 



In this preliminary notice the author does not devote much attention 

 to the egg membranes. What he says about the inner egg membrane 

 coincides with the views which I have expressed. He says that it " is 

 not composed of two layers either in Lepidosteus or in the sturgeon. It 

 is a simple zona radiata, the striae reaching to the innermost portions of 

 the membrane. The division into two layers, sometimes seen, is the 

 optical effect of thick sections." 



I cannot agree with his conclusions regarding the external layer, and 

 am confident that his final paper will not contain proof of the accuracy 

 of his statements. He says : " The pyriform bodies are certainly modi- 

 fied cells, each with the remains of a nucleus at its outer end. These 

 modified cells have degenerated into a sort of glue, which causes the ex- 

 cessive stickiness of the newly laid eggs. ... In the ovarian egg these 

 ' pyriform bodies ' are probably nutritive cells to the ovum, for their 

 outer ends near the nuclei contain a number of minute yolk particles." 



As far as regards the external layer, it is difficult to conceive how 

 our views, whether morphological or physiological, could have been 

 more divergent. 



