382 H. s. Pli ATT, 



he corroberates Willemoes-Suhm in certain respects. He also reports 

 that the parasite bores its way into the Copepod from outside entering 

 it between two thoracic joints or between the abdomen and thorax. 

 He has, undoubtedly, as Willemoes-Suhm, seen Copepods with the 

 worms projecting out of their sides into the sea-water, and come to 

 the same conclusion as that author that they were entering from 

 without instead of that they were breaking their way out from within. 

 It is indeed, difficult to understand how he could have made such a 

 deduction as his material contained Copepods which were still infected, 

 that is, which still contained their parasites, and these did not 

 show broken body-walls or any other injuries which would 

 necessarily result from the entrance into them of such large worms. 

 As already stated Giesbrecht sent some of his material to Monti- 

 CELLi for identification and that author represents in his fig. 6 one 

 of these infected Copepods, the body- wall of which is entirely un- 

 injured. I will add that the reason why Willemoes-Suhm and Gies- 

 brecht found so many Copepods, with these worms projecting from 

 their sides has already been given in this paper (see within pag. 353) : 

 it is that the elastic, chitinous cuticula of the Copepod pinches and 

 holds for a while the escaping worm, which, however, always finally 

 frees itself and emerges into the sea-water. I may also repeat what 

 has already appeared in the "Introduction" that I have, in a number 

 of instances, observed the whole operation take place. I have seen a 

 worm in the body-cavity of a Copepod, the body-wall of which was 

 uninjured and whole; I have then seen the worm, after repeated 

 efi"orts, thrust itself through the body- wall and project partly into 

 the surrounding water, sometimes the anterior and sometimes posterior 

 end being the one thrust out; I have then seen it after further 

 struggles pass, free, into the sea-water. 



On the morphological significance of the Appendix. 



Whether or no the appendix of appendiculate Distomes is homo- 

 logous to the cercarian tail is a question which has long concerned 

 helminthologists. Wagner (1860) and Leuckart are of the opinion 

 that the homology does not exist. Monticelli (1890, p. 23) has 

 recently declared himself in favor of it. His conclusions are, however, 

 based largely on the mistaken observations and deductions of Wille- 

 moes-Suhm, above quoted, and hence are not well founded. He refers 

 to the statement of that author that the worm while free-swimming 

 leads a predatory life, and makes its way into Copepods to float about 



