56 ILLINOIS BIOLOGICAL MONOGRAPHS [344 



to be the points of entrance of nutriment. The thickness of the cuticula, 

 according to the same author, is 19/x, an outer irregular layer being 5/i and 

 showing a sort of ecdysis ("Hautungsprocess"). Tliis, however, may be 

 simply the separation of the outer layer of the cuticula from the inner which 

 often appears in sections, since he said, "Diese Auffassung wird dadurch 

 erhartet, dass sich an einigen Stellen dieser Belag nicht findet, dafiir eine junge 

 homogene Cuticula, " — the latter being then the inner homogeneous layer. At 

 any rate, it is quite evident that the cuticula of C. truncatiis is a much thicker 

 tissue than that of the form described here — and no one else than Kraemer 

 seems to have described it. 



The subcuticula is comparable to that of C. truncatus in that it varies in 

 thickness from 25 to 40;U. It is composed of considerably elongated columnar 

 cells whose nuclei, Sju in diameter, are as thick as the cells themselves. Scat- 

 tered spaces in the loose parenchyma, which e\'idently accommodated cal- 

 careous bodies before they were dissolved in the fixing fluid, were found to be 

 ellipsoidal to almost spherical in shape and to vary from 13 to 2S}x in length 

 by 7 to 18 in width. Linton stated that the calcareous bodies of C. truncatus 

 are 10 to 20// long, Zschokke that they are 8 to lO/x and Kraemer that their 

 size is 30 by 18/x. 



In general the musculature is as described by Kraemer, but all the groups 

 are comparatively weakly developed (Fig. 82). The longitudinal layer, for 

 instance, is only 2Qp, in thickness in the median line posteriorly and about 60// 

 in the neck region (76/t in C. truncatus) where the dorsoventral and transverse 

 fibres are a,lso much stronger than elsewhere. In the anterior part of the neck, 

 particularly immediately behind the scolex, the fibres of the tvv'o latter series 

 are much stronger, altho less numerous than farther back. Just ahead of the 

 posterior end of the funnel they become arranged in an arcuate manner longi- 

 tudinally as well as transversely. Then from there on to the tip of the scolex 

 they gradually becom.e more numerous as they concentrate around the funnel 

 of the organ, of which they obviously act as constrictors. Antagonizing these 

 are numerous weaker radial fibres, arranged as in C. catenatus Riggenbach 

 ( = DiplocotyIe rudolphii Mont.) where they were considered by Riggenbach 

 (1898:639) to be derived from the longitudinal muscles with which they are 

 continuous at the base of the scolex. Altho they mingle freely among the 

 latter, they are still quite separate from them. Thus the writer is inclined to 

 the same view regarding their homologies in C. americanus, since it seems clear 

 that the dorsoventral and transverse fibres, which might otherwdse be con- 

 sidered to give rise to them, become modified to form the circular muscles of the 

 scolex. As a matter of fact only a very few of the longitudinal muscles of the 

 neck pass for a short distance beyond the bottom of the funnel; most of them are 

 inserted in the latter, thus functioning with the radial fibres in enlarging the 

 organ of adhesion. According to Riggenbach these radial muscles are ap- 

 parently absent from C truncatus. They were not described by Kraemer; but 

 the enlargement of the funnel was considered to be accomplished by the con- 

 traction of the dorsoventral fibres (cf. his Fig. 1). The outermost layer of 



