ANNULOSA: T^ENIADA. 231 



an example of true segmentation, nor do they really constitute 

 the Tape-worm ; the true animal being found in the small, 

 rounded, anterior extremity, the so-called " head," or " nurse," 

 whilst the joints are simply hermaphrodite generative segments, 

 which the " head " throws off by a process of gemmation. The 

 "head" (fig. 114, 3, and fig. 113, e), which constitutes the real 

 Tape-worm, is a minute, rounded body, which is furnished with 

 a circlet of hooks or suckers, or both, whereby the parasite is 

 enabled to maintain its hold upon the mucous membrane of 

 the intestines of its host. No digestive organs of any kind are 

 present, not even a mouth ; and the nutrition of the animal is 

 entirely effected by imbibition. The nervous system consists 

 of two small ganglia, which send filaments backwards; but 

 there is considerable obscurity on this point, and it has been 

 asserted that the nervous system is entirely wanting, or that 

 there is only a single ganglion. The " water- vascular system " 

 consists of a series of long vessels which run down each side 

 of the body, communicating with one another at each articula- 

 tion by means of a transverse vessel, and opening in the last 

 joint into a contractile vesicle. It thus appears that all the 

 joints are organically connected together. Whilst the "head" 

 constitutes the real animal, it nevertheless contains no repro- 

 ductive organs, and these are developed in the joints or seg- 

 ments (fig. 114, 3, and fig. 113, ti), which are produced from 

 the head posteriorly by budding. After the first joint, each 

 new segment is intercalated between the head and the seg- 

 ment, or segments, already formed \ so that the joints nearest 

 the head are those latest formed, and those furthest from the 

 head are the most mature. Each segment, when mature, con- 

 tains both male and female organs of generation, and is there- 

 fore sexually perfect. To such a single segment (figs. 114, 4, 

 and 113, h\ the term "proglottis" is applied, from its resem- 

 blance in shape to the tip of the tongue. The ovary is a 

 branched tube, which occupies the greater part of the pro- 

 glottis, and opens, along with the efferent duct of the male 

 organ, at a common papilla, which is perforated by an aper- 

 ture, termed the " generative pore." The position of this pore 

 varies, being placed in the centre of one of the lateral margins 

 of the proglottis in the common Tape-worms of man ( Tania 

 solium and T. mediocanellata), but being situated upon the flat 

 surface of the segment in the rarer Bothriocephalus latus. 

 These two elements namely, the minute head, with its hook- 

 lets and suckers, and the aggregate of the joints, or proglot- 

 tides together compose what is commonly called a "Tape- 

 worm," such as is found in the alimentary canal of man and 



