CLAM FISHERY OF PA88AMAQU0DDY BAY 



27 



SESSIONAL PAPER No. 22a 



minute worms like Planarians and Nematodes, the larvse of larger worms, little Crust- 

 acea like Cyclops and Cypris with cast-oflf appendages of larger forms, insects like mites, 

 ova and the larvae of various salt-water animals. Diatoms, from their abundance and 

 constancy of occurrence, may be considered the chief article of food. Experiments have 

 been carried on with a view to discover whether clams exercise any selecting power 

 over the food offered them. Finely divided flesh of fish or of shrimps was brought to 

 • the open siphons of living clams and let drop so as to be carried inward by the inhalent 



current with the result that the clams would close their siphons, or if at first accepting 

 the food it would be instantly expelled ; but when instead of fish or shrimps, diatoms 

 were used the clams would continue to accept them. 



REPRODUCTION — SPAWNING. 



Until quite recently little attention has been directed towards the time and 

 character of the spawning of the clam. It has been stated on the one hand that the 

 clam spawns in September and October ; on the other hand this was said to take place 

 in June and July ; only last year was published the statement that the clam spawns twice 

 each season. Again, statements have been made in an authoritative style concerning the 

 care of the brood, where it was clear that the author was judging by analogy with fresh 

 water forms possessing considerable differences in structure, habits and environment, 

 instead of describing from observation. During last summer I examined clams 

 every week from the 20th June to the 25th September, and I never found any with 

 ripe ova or sperm. I had concluded that their spawning time was early in the season, 

 perhaps in May, which also seemed to be borne out by the presence of small clams that 

 were to be procured in the sand at certain places at the very time when, according to 

 one statement, the mature clams should have been spawning. Since the completion of 

 my observations I have received a copy of a report by A. D. Mead, entitled, ' Observa- 

 tions on the Soft Shell Clam ' (reprinted from the 13th Ann. Report of the Comm. Inl. 

 Fisheries, Providence, R.I., Jan., 1900), in which from a study of clams in Narragansett 

 Bay during the summer of 1899, the author was able to write : ' The exact limits of the 

 egg-laying period of the clam have not been determined, but it probably extends through 

 the months of May and June.' He examined clams on the 8th and 12th May, and 

 found them full of sexual products that appeared to be nearly ripe. On the 22nd May 

 he was able to fertilize eggs from a female by adding to the water in which they were 

 kept some sperm taken from a male, and he followed the early stages of development. 



As the author of the above report does not describe the sexual elements, and as I 

 have not studied the ripe elements of the clam on account of not having been on the 

 spot early enough in the season, I shall here insert some observations I made on the 

 horse mussel {Modiola modiolus). This species, although more closely related to the 

 edible mussel {Mytilus edulis) than to the clam, yet resembles the latter in its habit of 

 burrowing its anterior end into the gravel, while the edible mussel fastens itself on the 

 exposed surfaces of rocks. The horse mussel is less common in Passamaquoddy Bay 

 than either the clam or the edible mussel, and finds fewer localities that offer it suitable 

 accommodation. Generally, it may be expected near low water mark, in the bottoms 

 of gravelly pools left by the receding tide, and in such positions near the outlet of these 

 that, during the absence of the tidal water below there is a constant supply of salt 

 water from the pool above. Such places are easily found on the ' Point ' at St. 

 Andrews, at the entrance to Katy's Cove nearby, on Pendleton's Island and elsewhere. 

 This mollusk, belonging to the same family as the edible mussel, resembles it in the 

 shape of the shell, the absence of siphons, the free borders of the mantle, and the 

 possession of a byssus — a tangle of stout threads protruding from between the valves 

 and fastening it solidly to rocks, stones or gravel. It is frequently larger than either 

 the clam or the ordinary mussel, has a brown shell (whereas the other mussel has a dark 

 blue shell), and is generally more or less bearded on the sides, and often partly over- 

 grown by sea-weeds or other organisms. It was not until 1884 that the sexual 

 characters and reproductive elements were studied, in the common British edible mussel 

 by Professor Mcintosh, of St. Andrew's, Scotland. He found that there were male 



