ox A NEW HUMAN TAPE-WORM (BOTTTKTOCEPHALUS SP). '^JJ 



iiew ])r()gl()[ri(le.s, flie anterioi'ly sitiuited is ;il\v:iyy the shorter until the 

 norinnl len<:;th is attained by growth. Examining with a hand-lens of 

 Jow magnifying ])ower, onr attention was at once called to the focts 

 tliat the bonndai'ies of ])roglottides were not all alike in their shar])- 

 ness and de])ths of marginal indentation and that they succeeded one 

 anotlier with a certain degree of regularity. The differences are evidently 

 duo to the oldness or lateness of their formation, usually four or 

 live consecutive proglottides together f(.)rmed a grou]) or what might 

 conveniently be called a primary segment, terminated anteriorly and 

 posteriorly by much better defined proglottidal boundaries. In 

 other words, every fourth or fifth boundary was genei'ally the most 

 pronounced and presumably the oldest formed. Where four proglot- 

 tides made up such a ])riniary segment, the boundary between its 2nd 

 and ord proglottides was usually the next well-deiined, whereas that 

 between the 1st and :^nd and also that between the ord and -fth were 

 com])aratively somewhat less sharply ])ronounced. We m.ight inter- 

 pret this so, that such a primary segment is composed of two 

 secondary segments, each of which again consists of two tertiary 

 segments or proglottides. Often the front ])roglottis of a ])rimary 

 segment had more or less distinctly divided into two, at 

 apparently a quite late period, in which case that primary segment 

 seemed to consist of five, instead of four proglottides. Sometimes the 

 next tertiary proglottis also showed signs of a similar t|uaternary 

 division. Thus then, within a given primary segment, the 

 division of ])roglottides takes place successively backward beginning 

 from the foremost proglottis. This corresponds to the fact already 

 mentioned that in an individual proglottis division occurs at 

 its anterier jiortion. It is easy to conceive that by a continued 

 process of such division, an individual proglottis would in course 

 of time come to rank as a secondary and this again as a jirimary 



