104 Transactions of the Royal Canadian Institute 



diameter of the eggs for any month is the average of the diameters found 

 for the ten individuals. 



The table above gives the date, the kind of haul, the number of 

 Sagittae taken, the lengths of those examined (which may be regarded 

 as typical of its entire number, as no special size was chosen), the average 

 diameter of the eggs, and the diameters of the largest eggs. 



A consideration of the facts given in this table leads to the conclusion 

 that the spawning season is a long one, extending from the end of March 

 or the beginning of April to September at least. September 4 would 

 seem to be near the end of the season, as at that time a, smaller proportion 

 of the individuals contained large eggs than previously. 



The diameters given cannot be taken as an accurate measure of the 

 size of the eggs, as the eggs are compressed and distorted into unspherical 

 shapes in the ovary, and for convenience the largest diameter was 

 always measured. Hence the actual diameter of the free egg would 

 probably be somewhat less. 



Identification of the Eggs in the Plankton. 



A first examination of material from the Bay of Fundy for the eggs 

 of Sagittae was fruitless, so an examination was made of material from 

 "Prince" station no. 30 in the Gulf of St. Lawrence, off Cheticamp, 

 Cape Breton island, where the young are known to be abundant during 

 late spring. Weekly hauls from May 23, 1917, to July 11 of the same 

 year were examined, and eggs were found which appeared to be those 

 of Sagitta. The first ones recognized contained embryos coiled twice 

 within the membrane, with the head slightly broader than the body. 

 One was removed from the membrane and examined beneath the micros- 

 cope, and the characteristic small black eyes of Sagitta were plainly 

 discernible. They were also occasionally recognizable in the embryo 

 within the egg. An examination of the earlier stages of the same eggs 

 found in the hauls showed that the gastrula displayed the tripartite 

 appearance due to the early development of gonads, which is typical of 

 the eggs of Sagitta. 



The diameter of the eggs — roughly about one-third of a millimeter — 

 corresponded with the size expected from measurements of eggs within 

 the ovary, and the length of the final embryo was approximately the 

 same as that of the smallest Sagittae found. Hence it was concluded that 

 the eggs must be those of S. elegans, the only Chaetognath occurring in 

 that place. 



At station no. 30 (see Table II) eggs were present in large numbers in 

 May, and probably also in April, but disappeared in the middle of June. 

 Three arbitrary stages in the development of the eggs were chosen, and 



