ANNELID GENUS CAMBARINCOLA — HOFFMAN 343 



size and proportions and confined to the ental third of the bursa. 

 Ejaculatory duct broadest ectally, merging gradually into penial 

 sheath; en tally it becomes narrower and is rather short in total length. 

 Spermiducal gland long and slender, curving cephalad and then 

 abruptly ventrad, extending down as far as level of penial sheath, 

 frequently with a small fairly distinct posterior deferent lobe visible 

 near the ental end. Prostate long and slender, half the diameter 

 of the spermiducal gland or less, but extending ventrad to the level of 

 the ental end of the latter, with a small but distinct terminal bulb. 



Spermatheca without specific peculiarities, consisting of the slender, 

 elongate ectal duct extending about one-third the way up one side, 

 a fusiform ental bulb, and a distinct, fairly large glandular ental 

 process. 



Variation. — The allegedly great variability of what has been 

 identified under the name philadelphica has become almost legendary. 

 Ellis (1919) gave the idea its momentum in remarking that material 

 from Douglas Lake, Michigan, occasionally has a dental formula 

 higher than the usual 5-4 (presumably 7-4 or 7-6), and that the 

 lobation of the peristomium was to some extent a function of their 

 extension or contraction at the time of death. Now these remarks 

 are perfectly in order, reflecting nothing more than one might expect 

 in the line of individual and ontogenetic variation, but Ellis con- 

 cluded by saying " Cambarincola philadelphica was the most variable 

 species studied," and his words like those of many another pioneer 

 were misused by his followers. 



We now know that Ellis unfortunately mixed several species under 

 his concept of philadelphica, including mesochorea and jallax. But 

 his concluding statement was picked up by Goodnight and even used 

 out of context to justify the relegation of C. okadai to the synonymy 

 of 2)hiladelphica. 



The foregoing preamble is not meant to deny variability within the 

 limits of philadelphica, but to indicate that previous ideas on this 

 score had little factual basis. 



In the large amount of material available, I found that the species 

 here identified as philadelphica is a rather plastic and complicated 

 ensemble of microraces and incipient subspecies. Owing in part, 

 at least, to differences in the way the crayfish hosts were preserved, 

 there is a dismaying range in the size, shape, and proportions involved. 

 However, in the most general terms, one can recognize fairly well- 

 defined populations on the basis of body form, these to be mentioned 

 in their turn. There is little appreciable difference in the reproductive 

 systems, notably some variation in the overall size of the male organs 

 which in some scattered localities tend to occupy more of the coelomic 

 cavity than is typical for the species. Whether this reflects the 



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