BULLETIN OF THE :ri> STATES PISH COMMISSION. 175 



of the oyster, polar globules being expelled in about the same position 

 as in the egg of the latter, the cleavage being also very similar. 



An important morphological point, namely, the precise mode of gas- 

 trulation of the embryos of this form was not definitely determined, but 

 it is inferred that in this respect tlie developing embryo of the clam 

 does nut differ essentially from that of the oyster. The development of 

 this njollusk was followed, at the time mentioned, as far as the swim- 

 ming or veliger stage, beyond which it was found difficult to keep it 

 alive by any means then at the command of the writer. Whether arti- 

 ficial methods of multiplying this form will ever be satisfactory seems 

 very doubtful, but it is obvious that a very simple method may be found 

 available for the purpose of obtaining the young of the clam for the 

 purpose of transplanting the species to new localities to which it is a 

 stranger. This conclusion is supported by the following data obtained 

 in connection with experiments conducted at Saint Jerome's Creek Sta- 

 tion in the course of the work at that place on the oyster. These inci- 

 dental observations show that the animal grows quite rapidly in the 

 course of a few months so that specimens from 1 inch to over 2 inches 

 in length may be expected in about seven months after the spawning 

 season is over, or during the next spring. This has been ascertained 

 as follows : 



During the month of February, 1884, a number of ponds were. exca- 

 vated at Saint Jerome's Creek in marsh land for the purpose of oyster 

 culture. These, after serving their purpose for the latter object, were 

 allowed to remain open to the outside water more or less during the 

 autumn, or from September onwards, and it is presumed that in this 

 way swimming embryos of the clam found their way into the inclosnres 

 from the outside. That such embryos could not have obtained access 

 in any other way is proved by the fact that the ponds were dug out 

 upon high ground where there had never been any clams before, so 

 that the only possible way in which the young clams could get into the 

 ponds must have been in the way described, the embryos evidently de- 

 veloping from eggs naturally spawned by the adults found buried in 

 the sandy bottom of the channel feeding the ponds. The sexes are 

 separate in Mya, or confined to distinct individuals, and the eggs meas- 

 ure about one five hundredth of an inch in diameter, so that the veliger 

 or swimming stage would be represented by a very small organism in- 

 * deed. These embryos, after swimming about for some time, would then 

 settle down upon the bottom, develop their characteristic siphon, and 

 bury all but the tip of the latter in the sand. In this situation their 

 growth must be quite as rapid, if not more rapid than that of the spat of 

 the oyster, which, in the space of five months, may grow to the length of 

 2 iuches. Such a rate of growth for the clam is indicated, by the size of 

 living specimens obtained from the bottoms of the ponds mentioned 

 above, when the latter were deepened in May, 1885, or about seven 

 months after the last spawning season of the species, which was in Oc 



