§4 SPAWNING DATA. Explanatory of Tables III and Illa. Tables III and IIIa exhibit data pertaining to the spawning of oysters at Barnegat, and at Tuckerton, respectively. As regards the place where the oysters were found, the following abbreviations obtain: "Anch," off Shad Point; "Cox," Cox's Cove; "E. L. C.," East of Little Cat Island; "Inlet," at the junction of Bay and the Lagoon exit; "Club," in the Bay, off the Hancock Club house; "BC," Big Cat Island. At Edge Cove, "Lab" means oysters growing near the Laboratory; "Mull," oysters from the mouth of the Mullica from planted beds, and transplanted to Edge Cove near the "Cynthia"; "GB," Great Bay plants; "Tank" refers to oysters both native and plants, kept in a tank into which the tides came twice daily. The capital letters indicate stations used in gathering the "fry" samples. "M" stands for Mullica, "Speck" indicates Great Bay oysters furnished by Captain James Speck. In the column headed "Size No." the whole number of oysters opened is indicated classified into large, medium and small sizes, the latter one or two years old, the medium three or four years old, and the large ones more than four years old. The number of males and of females was determined of each class, and their condition as to progress of spawning noted. "Spw'd" indicates spawned out; "prt," partly spawned out; "mot," motile sperms; "nr" nearly ripe or nearly spawned; "pl" planted oysters. Spawning Phenomena. Studying the Barnegat record as to spawning, we find that about half of the oysters examined at the middle of June had begun spawning, and as half of the fry in the water were half grown at this time, it is evident that the best eggs had been ejected for some time. A surprisingly large proportion of oysters passed through the hot period of June 25th without spawning, probably because they were not mature and the period was too brief to complete the work. Usually the first week in July is extra hot, and had this been the case this year, these oysters would have spawned normally. Speaking in terms of the experience of the ancestors of these oysters, they were justified in waiting for this expected weather, but they were doomed to disappointment. The weather turned cold, the water became cooler and the ripening processes were repressed. The holding back of these eggs was injurious. They gradually decomposed, as shown by their granular appearance. Towards the end of July we have indications of renewed spawning, and after August 2, it is hard to find oysters with sufficient spawn left for fertilization experiments. Evidently, the warm spell beginning July 19th and lasting to the 27th, enabled the oysters that had not spawned in June to complete this process. Turning now to a consideration of the spawning data at Edge Cove, we find that oysters were nearly through spawning at June 28th, though there was little to show for it in the way of swimming fry. This refers to the "natural" adult oysters of which there were fewer than usual, as most had been planted out in the Bay during the preceding Autumn. Perhaps this explains the general absence of fry at this time. The planted oysters, however, had not begun spawning, judging from a limited investigation early in July, but an examination of the plants July 18th, indicated that spawning had begun, and this tallies with the increased number of fry found. From this time, on well into August, it was increasingly easy to find oysters filled with ripe spawn. Naturals put into a special tank, became filled up again with spawn. The Great Bay plants transferred to Edge Cove near the laboratory, also became well filled. Oysters containing spawn, as well as those that had partly spawned, were easily obtained even during the period when the abundance of fry in the water showed that spawning was active. The plankton record of the latter part of August was proof that the oysters that held onto their eggs during early August, emitted them later. There was a peculiar continuity of spawning, new broods, small in number, being started every few days. There is reason to believe that these fry were weak and that very few came to the spatting stage. In fact, the conditions that favor a strong set of spat, are those that cause oysters to spawn en masse, quickly. |