78 



DEPARTMENT OF THE NAVAL SERVICE 



6 GEORGE V, A. 1916 



playing on it. The object was to maintain as uniform a temperature as possible. 

 Seventeen days after, all were alive. Records of shippers and experiments performed 

 at the station prove conclusively that large clams are less resistant than small ones. 

 Lot No. 1 was half and half, but lot No. 2 was all large. The contrast between these 

 two tests may be better seen in tabular form as follows: — 



That ventilation and uniform temperature are essential is here strongly empha- 

 sized, s 



Those dying in the course of these studies were microscopically examined, but 

 no cause of death could be discovered. The bodies wer.e wasted, parts shrunken, and 

 the whole general appearance that of an animal dying from enervation due to a lack 

 of nourishment. Generally speaking, no ripe generative elements were found, they 

 had either been shed, or failed to develop into large, sound ova or sperm. In some 

 instances, however, ripe ova and sperm did occur in small quantities, sometimes in 

 the reproductive organs, oftener in the branchial chambers, where the ova were break- 

 ing down or disintegrating in the midst of swarms of bacteria and some protozoa. 



It is the general belief that the valves of a clam spring apart at death, the adductor 

 muscles relaxing, but such does not seem to be the case, for an immediate examina- 

 tion found decomposition already under way, accompanied with an offensive odour. In 

 the case of such a low organism it does not seem possible to define death as a separate 

 act, for the various parts and organs do not cease their functions simultaneously, and 

 the muscular tissue of the adductors, the strongest in the body, may be the last to do 

 so. In this connection it may be noted that the consignees at Chicago maintained the 

 clams were dead on arrival, though the valves were unopened, but when opened in the 

 usual way, they were unfit for use. 



It is difiieult to account for the decomposition of the ova. Though the clam 

 possesses great resistance to a lack of oxygen, ova, especially when fertilized, demand 

 a medium rich in that element, and renewed constantly. Lacking these conditions, 

 the ovum generally dies and begins to decay, and where, as in the clam, it is in close 

 contact with the most delicate and exposed part of the vascular system, certain toxic 

 efi'ects, fatal to the animal, may result. To this cause may be attributed, in part at 

 least, the high death-rate of shipment in July, probably the maximum spawning 

 period. The small clams were then nearly immune, and it is significant that ripq 

 reproductive products were found in only one small individual at the station. Had 

 this class already spawned, or not reached the necessary age and development? This 

 question could not be answered at the station, nor could any definite information on 

 the point be obtained from the scientific literature available. Its determination would 

 be of some economic value to the trade, and conservation of the fishery. , 



In closing the brief report of this investigation, the following recommendations 

 might seem warranted by the facts disclosed, and some at least could be tried at little 

 extra cost over present methods. The trade should seek, as far as possible, to mini- 

 mize the general loss, maintain the reputation of its goods on the market, and at the 

 same time prevent the recurrence of such enormous losses as those met in 1914. 



