436 GROWTH AND STRUCTURE OF "LENTA SAG IN AT A. 



homologous rostellum of the hooked tape-worms agrees in every parti- 

 cular with a sucker ; yet although this is as clearly stated in my former 

 observations, as now, Kiichenmeister seems to have misunderstood my 

 comparison of the two structures, for he characterises it in his recent 

 work on parasites sometimes as "unfortunate" and sometimes as 

 "incorrect." I can hardly suppose that these epithets will utterly 

 condemn the alleged homology, for this has been, as Moniez em- 

 phasises, established beyond doubt by the developmental history. 



The black coloration, which was long ago observed by Andry, and 

 which occurs much more abundantly in Tcenia saginata than in T. 

 solium, is caused by a granular pigment which is embedded in the 

 connective tissue, and is sometimes found even within the cells. 

 Here and there, according to Virchow, it has a crystalline character. 

 Where it occurs only sparsely it is usually found restricted to the 

 neighbourhood of the suckers, but is sometimes spread over the whole 

 head. Davaine describes as a special variety a perfectly black tape- 

 worm (" Tenia negre ") from the Southern States of North America, 



As to the nature of this pigment, nothing certain is known ; but it 

 is probable that it originates from the colouring matter in the blood 

 of the host, and therefore has the same origin as the pigment of the 

 latter, having a close resemblance to melanin. Its origin can hardly be 

 as simple as Kiichenmeister would have it, when he supposes that 

 those blood-corpuscles which are taken in by the pores of the suckers, 

 and are not used, become changed directly into pigment. 1 - This can 

 hardly be, for the ingestion of blood-corpuscles through the suckers 

 of the Tcenice is more than doubtful on anatomical grounds (p. 304) ; 

 and further, it must be noted, that this embedded pigment is found 

 occasionally even in the bladder-worms, that is, in organisms which 

 are hardly in a position to devour blood-corpuscles as such. In 

 Tcenia saginata, indeed, I have not yet noticed these black -headed 

 bladder-worms, but they are to be found in T. solium, which is, 

 however, on the whole much less copiously provided with the pig- 

 ment. For this reason I think I am justified in assuming that the 

 presence and distribution of the pigment stand in no definite relation 

 to the age of the worm. 



We have already noted that the pigment is not found exclusively 

 on the head, but occurs occasionally on the vagina, vas deferens, and 

 testes. This is the case, however, only in the older proglottides, 

 where the organs in question are no longer functional. 



In such ripe joints one sometimes finds in the cortical sheath 

 accumulations of granular molecules, and also yellow fat-drops, some- 



1 Loc. cit., p. 151, note. 



