156 ENTOZOA. 



inch objective the precise mode of their final distribution is 

 readily seen. The ultimate twigs lose that rigid, straight, 

 tubular character which the primary trunks display, and twist 

 somewhat irregularly, hke the mycelium of a fungus. The final 

 division is almost invariably bifurcate, in which case, however, 

 there is frequently much disparity as regards the relative length of 

 the divisions. In the foregoing woodcut, these appearances are 

 correctly given (a, a, Fig. 34). The coecal extremities are always 

 separated fi'om one another by an interspace more or less consider- 

 able, and the final twigs often appear to have gone out of their 

 way, as it were, in order to avoid the contingency of union. They 

 seem to say " union is impossible," and bend suddenly upon them- 

 selves, at an acute angle, to get out of the way of opposing vessels 

 coming from other directions (&, h. Fig. 34). 



Having succeeded with my injections of the water-vascular 

 system in numerous instances, I am in a position to speak pretty 

 confidently in regard to many of those points which have hitherto 

 been regarded as doubtful. It is quite clear that the ancient view 

 of Mehlis, as to the termination of this system by a caudal outlet, 

 is correct ; but it is not quite so evident that the ultimate coecal 

 ends of the excretory vessels have any connection with the so- 

 caUed calcareous corpuscles. These bodies, indeed, do not appear 

 to have any existence in the common fluke and its allies, although 

 they have been found so abundant by Wagener in the trematode 

 Holostomata. Possibly they may occur here in a very rudimentary 

 or incomplete state ; but if we subject any one of the ultimate 

 coecal ends of these vessels to high magnifying powers, we invari- 

 ably find (in the fresh condition) the extremity of the tube occupied 

 by a quantity of highly refi^acting yellowish corpuscles (the largest 

 measuring a^"), looking very like fat globules. It is difficult to see 

 any connection between these bodies and the calcareous corpuscles, 

 especially as they do not exhibit the same phenomena under the 

 addition of acid reagents. These highly refracting corpuscles 

 vary very much in size, some of them, according to Leuckart, 



