WIUJAM KEITH BROOKS — CONKUN 



these papers are : ( i : ) That the embryonic record of the Cephal- 

 opoda "has been simplified to a degree which is without parallel 

 in the animal kingdom, and it is hardly too much to say that 

 the ontogenetic process furnishes us with no knowledge what- 

 ever of the phylogeny of the group;" (2) that the yolk sac of 

 the cephalopod embryo is the homologue of the gasteropod 

 foot; (3) "that if the epipodal folds of the gasteropod are re- 

 garded as homologous with the cephalopod siphon, the arms 

 of the cephalopod must be regarded as independently acquired 

 structures; whereas if we regard the arms as modifications of 

 the epipodal folds, we must consider the four siphon folds as 

 independently acquired structures;" and (4) "the common 

 ancestor of the gasteropods and cephalopods must have been 

 an unspecialized form, and we cannot expect any valuable re- 

 sults to follow from the attempt to compare any part of the 

 body of a cephalopod with structures which, like the epipodal 

 folds, are not common to the Gasteropoda, but somewhat ex- 

 ceptional." 



All his other publications on the Mollusca, fourteen in num- 

 ber, deal with the development and propagation of the oyster. 

 In 1878, during the first session of the Chesapeake Zoological 

 Laboratory, he attempted to find young oysters in the gills of 

 the female, as had been described in the case of the European 

 oyster, but without success. In May, 1879, he went to Cris- 

 field, Maryland, the center of the oyster industry on the Chesa- 

 peake, and settled down to study the problem of the develop- 

 ment of the oyster. "On Monday, the 21st," he says, "I 

 opened a dozen fresh oysters, and found three females, with 

 their ovaries filled with ripe ova, and one male, with ripe sper- 

 matozoa. I mixed the contents of the reproductive organs of 

 these four oysters, and within two hours after the commence- 

 ment of my first experiment I learned by the microscope that 

 the attempt at artificial fertilization was successful, and that 

 nearly all of my eggs had started on their long path toward the 

 adult form. ... I have accumulated enough evidence to 

 show, beyond the possibility of doubt, that so far as the oysters 

 of the Chesapeake Bay, during the summer of 1879, are con- 

 cerned, the eggs are fertilized outside the body of the parent, 

 and that during the period which the European oyster passes 



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