1914] A New Cestode from Amia Calva L. 113 



oncosphere up to the small process, situated a short distance from its 

 tip (Fig. 32), This process and the slightly swollen central end of the 

 hook seem to act as bases of attachment for what appears to be a well- 

 developed musculature actuating them. The hooks again approach 

 and the whole cycle is completed. In the most vigorous specimens these 

 movements take place at the rate of about three per minute. As might 

 be expected, the slightly smaller anterior end is much affected by the 

 movements of the other end ; however, it exhibits movements of its own, 

 consisting of small waves of contraction commencing at the inner ends 

 of the hooks and passing forward, thus in a direction opposite to those 

 seen in the plerocercoid and in the young strobila. 



Concerning the life-history of this species nothing can be offered at 

 the present. It was only noticed, as mentioned at the outset, that 

 plerocercoids a few millimeters in length were found in the intestine of 

 the host along with the largest strobila taken. The food of Amia calva 

 consists, however, evidently entirely of small fish, mostly minnows, and 

 it is possible that one or more species of these are the intermediate hosts. 



Summary. 



The form of the body of this worm is peculiar in that proglottidation 

 is expressed externally only in the anterior end of the strobila, beginning 

 immediately behind the scolex. Here the proglottis is provided at its 

 hinder end with four ear-like appendages directed posteriorly, which, in 

 conjunction with their fellows of the neighbouring joints, may act as 

 important accessory organs of attachment, perhaps by forming temporary 

 suckers or using certain rows of spines, arranged around their edges, to 

 obtain a hold on the mucous membrane of the host's intestine. Pos- 

 teriorly these appendages disappear, leaving no indication of proglot- 

 tides apart from the sets of reproductive organs which follow each other 

 at regular intervals in the usual manner. 



The scolex differs little internally as well as externally from the fore- 

 most joints, the two bothria or suckers being comparatively feebly 

 developed. 



The musculature is particularly well expressed in the jointed region 

 of the strobila which is consequently the most mobile. All of the usual 

 groups of muscles to be seen in Bothriocephalids are present, the external 

 longitudinal fibers being quite distinct from the inner or longitudinal 

 muscles of the parenchyma but confined to the anterior end only of the 

 strobila, while the outer transverse series is divided into two sets on each 

 surface of the proglottis, the fibers of which are directed postero-laterally 

 and thus made to decussate in the mid-line. The individual fibers of 

 nearly all of the groups of muscles are characterized by having their 



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