48 DEPARTMSyT OF THE IS'ATAL SERVICE 



6 GEORGE V, A. 1916 



The young of nearly all animals are more liable to such diseases than the adults. 

 In Canada about thirteen babies die during the first year out of every 100 that are 

 born; but nevertheless about three babies out of every four grow into men or women. 

 In the case of lobster babies, however, only one out of every 15,030 grows into an 

 adult. The inexorable forces of nature in the shape of cold, famine, and disease kill 

 off the young by millions. 



Whence came the parasitic plants from the growth of which our larva? died? 

 The answer to this question lies at the very rcot of our failure to rear larvae. Did 

 they come from the pond water, or did they come from the mother lobsters? A physi- 

 cian when looking for the origin of a case of scarlet fever would first ask whether 

 any other member of the family had previously suffered from the disease. If not, he 

 would look for some point of contact between the patient and jome outsider who had 

 been previously ill with the disease. Similarly, the staff at Long Beach cast about 

 for the possible source of infection. Yery early in our first experiment the micro- 

 scope revealed the principal diatom adhering to the limbs of the larvae. Later on, its 

 growth on the limbs became so thick and " fuzzy " that any one could recognize it 

 with the naked eye, once it h;id been pointed out. 



Where did it come from? Search (under the microscope) among scrapings taken 

 from the legs and " feelers " of mother lobsters showed the presence of the four kinds 

 of parasitic plants. Here, then, was one possible source of infection. In hatching 

 out their eggs, the mother lobsters may have transferred the parasites to their yoiing, 

 just as a human mother may give an infectious disease to her child. 



The other sources of infection were, of course, the sea or the pond water. In 

 order to determine whether the parasitic plants come from the pond water, or from 

 the sea, tow-netting was carried on: (o) in St. Marys bay, and (h) in one of the 

 hatching boxes which had been raised, cleaned, and repainted. The examination of 

 the material obtained in this way, as well as the descriptions of the structure of the 

 diatoms and fungus, awaits the examination by experts to whom the material has 

 been sent, and who will report upon it in the near future. 



In one particular the parasitic plants which caused the death of the larvi« are 

 quite unlike those which cause infectious diseases among human beings. The former 

 rapidly increase in number when growing in the light, the latter are usually killed 

 off by the light. To keep diatoms, therefore, and other parasitic plants off mother 

 lobsters, they should be kept either in deep water into which comparatively little 

 light can penetrate, or they should be provided with artificial shelters from the light. 

 Sheltering from sunlight would not merely be conforming to the natural habit of the 

 animal, but it would be a means of lessening the parasitic growths upon them, and 

 therefore preventing the spread of growths to their young. 



An observation made by Williamson would appear to Explain how parasites might 

 grow profusely on berried lobsters between the time they reached the pond and the 

 time they hatched out their young in our hatcliing car: — 



" In each of the two large concrete tanks were placed two* female lobsters. 

 In one tank a board shelf afforded protection from the sun so that only the 

 antennsB of the lobsters were exposed to its rays. In the other tank there was 

 no protection from the sun whatever. In the first case, aftei- the summer 

 season was over the lobsters themselves were free from growths of all sorts, but 

 the antennte were covered. The bodies and appendages of the lobsters which 

 were confined in the exposed tank were, however, ciuite hidden by the prolific 

 growth of sea-weeds, laminaria, young mussels, etc." — (Quoted from the Report 

 R. I. Com., 207th Jan. Sess., 1906, foot-note to sec. xvi, ' Influence of Para- 

 sites.' ") 



A clear distinction must be made between the effect of diatoms on larvae and the 

 effect of a fungus growth. The former act mechanically and by clogging the limbs 



