244 Geary I na Siveet : 



shaped at the tip, and in side view bent dorsally. The dorsal 

 root is short, the ventral long, curved and pointed (contrast the 

 rostellar hooks of D. proglottiua). The suckers are circular, 

 .033 to .046 mm. in diam. (rarely the latter), and are armed 

 with 4 or 5 (or rarely 6) rows of thorn-like hooks, .005 in 

 length, with a more or less clearly bilobed base, formed by the 

 two roots, which are almost equal in length. These hooks 

 become very easily detached from the suckers (as shown in Fig. 

 1). The strobila has in addition to the head from 4 to 6 seg- 

 ments, the shape of which varies greatly. The first may be 

 only .045 mm. long, and the last may be .29 mm. (in a strobila 

 of .7 mm. length) to .79 mm. (in a strobila of 1.32 mm. length). 

 The shape of each individual segment being much wider tluin 

 long (e.g., in the proportion of 4 or 6 to 1), may be such that 

 the whole strobila is like a low cone with a rounded base ; or, all 

 the segments except the youngest, from being equal in length and 

 breadth, may become at the posterior end \h to 2^ times as 

 long as they are wide. The head becomes very easily detached 

 from the first segment, and that from the second segment. 

 Genital pores are alternate, and situated at or near the anterior 

 angle, sometimes on a low papilla. The stage of development 

 reached by the female genitalia in relation to that of the male 

 in the individual segments varies in different individual strobilae. 

 Thus in some cases a condit'on somewhat similar to that found 

 in D. proglottiua is to be seen, i.e., the last segment contains 

 only the eggs with the oncospheres. The next younger segment 

 cf)ntains well-developed female organs, often with fully-formed 

 eggs, and the more or less atrophied male organs, while in the 

 next younger segment still, the female reproductive organs are 

 somewhat more developed than in the corresponding segment in 

 D. proglottiua. Two variations from this condition are found. 

 In the one the male organs appear to be functional as far back 

 as the fifth or last segment (e.g., Fig. 8), the female organs being 

 much less developed than in corresponding segments of other 

 strobilae. In the other variation hardly any sign even of 

 atrophied male organs can be seen in any of the segments, the 

 eggs being well developed as far forward as the third segment. 

 Evidently there is a considerable difference in the degree of 

 protrandry shown in different individual strobilae. 



