No. 528] SPAWN AND LARVA OF AMBY STOMA 733 



three years ago and found a small amount of spawn of 

 a type already familiar to him for some years from its 

 abundance in pools in other localities. But the greater 

 amount was of a type that differed from this in the 

 points detailed below. These two types have proved to 

 be the punctatum type and the jeffersonianum tyi>e, 

 respectively. The predominance of the latter subse- 

 quently found its explanation in the fact that 31 of the 

 33 individuals captured in the woodland since then have 

 been of the latter species. It is impossible to determine 

 accurately the proportions in which the two types of 

 spawn occur, but estimating roughly, the jeffersonianum 

 type is at least ten times as abundant as the other. 



As will appear below, a small percentage of the eggs 

 of A. punctatum will approach in size, or color, or mode 

 of deposition — but rarely in more than one of these 

 points at a time — the eggs of A. jeffersonianum. Con- 

 sequently, the separation of the latter as a type when 

 found in a pool where the punctatum spawn greatly 

 predominates, is not an obvious thing. But when the 

 proportions are reversed, as in the special pools men- 

 tioned, the distinction is most easily made. Observa- 

 tions in the field have agreed in all four seasons and 

 have been supplemented by the capture of females just 

 previous to egg-laying and comparison of mature ovar- 

 ian eggs and eggs laid by them in the laboratory, with 

 those obtained in the pools; and finally by the rearing 

 in the laboratory of larva? from the two types of spawn. 



The points of difference in order of constancy are as 

 follows : 



1. Size. — The eggs of A. jeffersonianum are distinctly 

 the smaller, the usual diameter being 2-2.25 mm. 



2. Color. — The eggs of A. jeffersonianum are much 

 the darker, the pigment being but little removed from 

 a true black and covering a much larger proportion of 

 the surface of the egg than in A. punctatum; even the 

 lower surface is usually as dark as the upper surface of 

 many of the eggs of the latter species. 



3. Time of Laying. — The deposition of most of the 



