10 DEPARTMENT OF THE NATAL SERVICE 



6 GEORGE V, A. 1916 



In 1913 a similar epidemic was observed; vast numbers of dead and dying fish 

 being noticed in June by the fishermen, before tlie annual run of spawning herring 

 had left the coast. Fishermen recalled a similar condition sixteen years ago. The 

 herring affected appeared to be the oceanic form, which visits Northumberland strait 

 in July for spawning purposes. The season was colder than usual, and the littoral 

 schools of herring were scarce. The diseased fish showed lateral sores in the tail 

 region, and a cavity was hollowed out beneath the "lateral line," and open in places 

 on the surface. Examination proved the presence of a N eosporidium, one of the 

 Myxosporidia, which spread by means of spores called " sporonts." Each sporont is 

 enveloped in a dense wall which dissolves in the stomach of the fish, after it has been 

 rfwallowed, and an " amoebula " emerges, which finds its way into the blood, and finally 

 to the various tissues and they thus become infected. The sporont appears to develop 

 into a multinucleate Plasmodium, which breaks up into " mer®nts," by a process of 

 budding, rather than by fission. The sporonts abound where the tissue is in a state 

 of disintegration, the planonts in the blood, liver, etc., and the meronts in the least 

 affected regions. Doubtless the sporont is the means, concludes Dr. Cox, of contam- 

 ination amongst the herring schools. 



Vlir. LIFE OF THE HAKE, A SCALE STUDY (mR. E. HORNE CRAIGIE). 



Mr. Home Craigie, Toronto, reports on the life-history of the hake as determined 

 by the scales. These scales differ from those of the cod, and bear some resemblance to 

 those of the salmon, the centre of the scale being usually a ring with a small anterior 

 break, or else it is a short spiral. It is probable that the lines of periodic growth are 

 annual, but that is undetermined. Most specimens seem to be three years old, and the 

 curves appearing in the " graphs " constructed during the researches, show fairly uni- 

 form growth, greatest in the first year and decreasing in later years. Hake appear to 

 spawn mainly in the fourth year and onwards, the spawning period being always one 

 of decrease in the rate of growth. ' 



Eemales are longer than the males, and are far more numei'ous; unless the latter 

 associate in separate schools. Of 942 specimens e:::amined only 214 were males. 



IX. GROWTH OF THE HADDOCK A SCALE STUDY (mISS D. DUFF). 



Miss Dorothy Duff, McGill University, summarizes her study on " The GrovTth of 

 the Haddock," in a report which presents many points of interest. The haddock, as in 

 other allied fish, spawns when it reaches its fourth, or possibly, its fifth year. The 

 rings on the scale, which indicate rapid growth under summer conditions, are wide, 

 but in winter narrower and more compressed. Each band of summer and winter 

 growth represents one year, and by counting the winter rings, the age can be esti- 

 mated. Growth of the scale is proportional to the growth of the body. Interesting 

 results were obtained when determining the weight of certain organs at different 

 stages of growth. The liver, for example, was 21 per cent of the total weight in some 

 instances, but in others, less than 1 per cent, and again in others 4 per cent. 



The size of the egg was studied, and it bears no proportion to the size of the 

 ovary, large eggs often occurring in a very small ovary. The eggs in a 4-year-old fish 

 were yi2-, inch in diameter ; in 6-year-old fish they were a fifth larger, namely, Moo inch. 

 The table at the end of Miss Duff's report is interesting, and shows that a 1-year-old 

 fish may grow to double, or even treble, its length by its second year, and similarly in 

 its third year, but increases only one-seventh or one-tenth in the fourth year; while 

 in the fifth year the increase may be one-eighth or one-fifth, and still less in the sixth 

 and seventh years. One specimen in its eighth year was one-thirteenth longer than 

 in its seventh year, and nearly six times the size it attained in its first year. 



