CELL CONSTANCY IN THE GENUS EORHYNCHUS 265 



diameter of 0.132 mm. and a short axis of 0.048 mm. while the 

 ventral nucleus ranges in size near 0.250 X 0.057 mm. Instead 

 of occupying a position posterior to the second dorsal nucleus, 

 as in Eo. gracihsentis, the ventral nucleus of this species is typi- 

 cally opposite the foremost of the dorsal series. A slight variation 

 does occur with regard to the relative location of the ventral 

 nucleus but this probably is due to difference in degree of con- 

 traction of various individuals. 



Eorhynchus emydis. Though the individuals of this species 

 are very much larger than those of either of the preceding species, 

 being from 3 to 32 mm. long, yet the number of nuclei in the sub- 

 cuticula is the same. Using the arrangement of the nuclei of the 

 subcuticula as a basis for argument it appears that the excessive 

 size of the species is brought about by an elongation of the poster- 

 ior region of the body rather than by a uniformly distributed 

 elongation. The evidence for this lies in the fact that, while the 

 two anterior dorsal nuclei remain relatively close together, the 

 three of the remaining group are separated from each other by a 

 marked interval. The ventral nucleus occupies a position op- 

 posite that of the foremost of the dorsal row, or, occasionally, a 

 little anterior to it. No variations of number or of arrangement 

 were observed in the numerous individuals of this species which 

 were studied. 



Eorhynchus cylindratus. Here, again, is found the typical 

 number of subcuticular nuclei. The distribution of the dorsal 

 nuclei closely approaches that found in Eorhynchus emydis 

 (Leidy), but the ventral nucleus more often takes a position mid- 

 way between the two anterior dorsals, approaching nearer to the 

 posterior of these than to the anterior as in Eo. emydis. The 

 distribution of the dorsals strongly suggests that found in the 

 preceding species. 



Eorhynchus tenellus. In this species, likewise, the five dorsal 

 nuclei and one ventral nucleus in the subcuticula have an arrange- 

 ment similar to that of Eo. emydis. 



