Reproduction in Sagitta Elegans 111 



Magdalen shallows, but we are not prepared to state which condition 

 is the normal one. Although eggs are produced for at least six months 

 of the year, from April to October, recently hatched young were found 

 only in the latter half of the period. Throughout the whole period, ex- 

 cept in September, the early embryonic stages predominated, indicating 

 an extremely high mortality of the embryos. Not only so but, with 

 the same exception, the young were either absent or extremely rare, 

 and these all recently hatched, indicating that the few that were hatched 

 did not survive long. Only in September did the picture brighten 

 temporarily. On the 4th of that month the hauls gave a preponderance 

 of the later embryonic stages, a rather large number of young, and some 

 of these with a length as great as 10 mm. This improvement seems to 

 have been without effect on the final result as on October 2nd not only 

 did the early embryonic stages again predominate, but there was no 

 indication of the survival of the young hatched in September. At 

 "Prince" station no. 5 the results were similar. 



The physical conditions at Station no. 3 as furnished by Professor 

 Vachon were, — the temperature rising from 2.27 to 12.19° C. at the 

 surface and falling again to 9.77° C, that at a depth of 10 metres being 

 somewhat lower; the salinity varying from 27.90 to 32.56 0/00 at the 

 surface, and from 30.99 to 32.56 0/00 at 10 metres depth; and the 

 density ranging from 1.02222 to 1.02604 at the surface and from 1,02396 

 to 1,02604 at 10 metres depth. 



It must be confessed that in spite of the general differences between 

 the Gulf of St. Lawrence and the Bay of Fundy, there is little in the 

 physical data for the stations and periods under consideration to con- 

 sider as responsible for the great difference in success in breeding in 

 these two regions. For both the range in temperature is so great and so 

 very similar as to make it necessary to exclude it as a factor. The 

 salinities and densities at station no. 3 were on the whole higher than 

 those at station no. 30, but not uniformly so. We are forced to conclude 

 that a factor that may be responsible for the differences has yet to be 

 demonstrated. 



As it has been shown definitely that failure attends the reproduction 

 of Sagitta elegans in the Bay of Fundy, the origin of the adult population 

 of the Bay must be sought elsewhere. Great scarcity of the young has 

 been found to obtain every year from the time (1915) when observations 

 were begun, up to the present. In the autumns and winters of 1915, 

 1916, and 1917, the adults were found in large numbers, but during the 

 following years they decreased, the lowest ebb being reached in the 

 spring and summer of 1920. The Chaetognaths do not maintain a 

 movement in any one direction, but dart somewhat aimlessly first in 



