es of Davaine, Salensky and others, who, however, have 

 failed to see the earliest stages. 



The note on the development of Mya arenaria is 

 added merely to establish the time of the spawning sea- 

 son ; to show that it is possible to impregnate the eggs 

 artificially, and to indicate to some extent the nature of 

 the process of development, the study of which I could 

 not complete owing to illness. 



The histology of the ovaries of both the oyster and 

 clam remains to be studied, since it is possible only by 

 that means to ascertain whether the whole of the eggs 

 are mature at one time. The researches of Flemming 

 and Yon Jhering show that such is not the case in Unio 

 and Scrohicularm. Much of the success of future 

 attempts at artilicial incubation depends upon a decisive 

 answer to this question. My own experience in investi- 

 gating the ovaries of Ostrea and Mya^ countenances the 

 belief in my mind, that the time of maturity for nearly 

 all the ovarian eggs is about the same. 



The question as to the exact age of the fry of the oyster 

 at the time of fixation, as well as the age of the fry of 

 Mya at the time it buries itself in the sand, also awaits 

 an answer ; but it is the hope of the writer that, with an 

 incubating apparatus which he has lately devised as an 

 adjunct to his microscope, he may in the course of another 

 season's work, reach a satisfactory conclusion in regard 

 to this, as well as many other important matters. 



