54') 



THE AMEBIC AN NATURALIST 



[Vol. XLVI 



as set at a different angle from the corresponding struc- 

 ture in the humped type, is here fused with the ramus 

 instead of being merely bent over inward from its outer 

 margin. Bui the tips differ most; the secondary lamel- 

 late teeth, as before mentioned, become very large, 

 though variable, structures. They always meet in the 

 middle line when the jaws are closed; they have wavy or 

 corrugated surfaces, and thin down to a sharp cutting 

 edge. The tips of the rami are modified most of all. 

 They are slender and greatly extended in length, meeting 

 and passing at an acute angle. Neither tip is bifid, and 

 the asymmetry between the two rami is much less 

 marked. The jaws do not interlock, when closed, in the 

 sense in which they do in the humped type ; instead, the 

 tips invariably cross, like the mandibles of a crossbill, the 

 farther closing being prevented by the meeting in the 

 middle of the lamellate teeth. Occasionally I have 

 noticed a campanulate whose jaws had sheared past in 

 the wrong way; the lamellate teeth then did not meet 

 to prevent farther closing, and the animal had apparently 

 lost control of the organs, as the two halves remained 

 crossed well down to near their bases. 



Returning to Rousselet's description of the trophi of 

 A. amphora, which must, of course, be compared only 

 to the trophi of the humped type, I will say that despite 

 the discrepancies in detail which I deem due to inaccuracy 

 of observation, it remains true, nevertheless, that his gen- 

 eral figure of the trophi of this species coincides essen- 

 tially with the general appearance of the trophi as I find 

 them in the humped and saccate types, and this con- 

 stitutes a fair reason for assigning, provisionally, the 

 material which I have studied to the species Asplanchna 

 amphora. 



I towever, I can not leave this matter of the trophi with- 

 out instancing a surprising observation which I have 

 made the past summer on the trophi of the related 

 species, Asplanchna b right ic ell i— an observation which 

 again complicates, in an entirely new way, the question 

 of species in the genus Asplanchna. 



