NATIONAL ACADEMY BIOGRAPHICAL MEMOIRS — VOL. VII 



the blastopore and the origin of the digestive tract; but since 

 his observations were made exclusively on living material, he 

 fell into several errors, mistaking the shell gland for the mouth, 

 which he maintained appeared opposite the original position of 

 the blastopore, and concluding that the macromeres fuse to- 

 gether, and afterwards bud out cells which form the alimentary 

 canal. In the main the same remarks apply to his "Prelim- 

 inary observations on the development of the prosobranchiate 

 gasteropods," which appeared in the same year (1879).* In 

 this paper, and in a subsequent one on the "Acquisition and loss 

 of a food yolk in molluscan eggs," he devoted much attention 

 to what is now known as the yolk lobe, or polar lobe, which he 

 regarded as a "food yolk." This he believed to be in process 

 of being lost in some cases, as, e. g., the oyster, while it was 

 being acquired in others. It is needless to say that this ex- 

 planation of this problematical yolk lobe is no longer found to 

 be satisfactory. In a brief paper on the "Development of the 

 digestive tract in molluscs" (1879) he reiterates his mistaken 

 view that in gasteropods and lamellibranchs the blastopore is 

 converted into the shell gland, and that the mouth forms at the 

 opposite side of the embryo. With the exception of a single 

 paper, published in collaboration with one of his students in the 

 last year of his life, this list comprises all of his publications 

 on the gasteropods. The paper just mentioned is. entitled 

 "The origin of the lung in Ampullaria" (1908), and is based 

 upon the study of material which he obtained on his trip into 

 the Everglades in 1906 (see p. 53). In brief, the conclusion 

 of this paper is that the lung of this prosobranch has no an- 

 cestral connection with the lungs of pulmonates. "The gills, 

 the lung, and the osphradium of Ampullaria arise simulta- 

 neously, or nearly so, and they must be regarded as a series of 

 homologous organs specialized among themselves in different 

 directions." 



During the second session of the Chesapeake Zoological 

 Laboratory material was collected for a study of the later 

 stages in the development of the squid, Loligo pealii, which 

 resulted in the publication of two papers, one "The develop- 

 ment of the squid," the other "The homology of the cephalo- 

 pod siphon and arms." The most important conclusions of 



58 



