FREE JOINTS, OE PEOGLOTTIDES. 



43 



Fig. 22. 



is shown by F. S. Leuckart, who, rightly appreciating the 

 true meaning of these jointed Cestodea, and yet apparently 

 not liking to oppose his contemporaries too strongly, merely 

 expressed himself thus upon the matter. 1 " I was almost inclined 

 to consider the jointed tape- worms as organisms, in which each 

 joint is a separate animal, and the whole a compound animal, as 

 has been before supposed by many distinguished zoologists." 

 Steenstrup returned to the idea (loc. cit., p. 103) that the tape- 

 worms are compound animals, and subsequently, Van Beneden 2 

 in his admirable monograph, has pointed out and illustrated with 

 excellent figures many striking and conclusive examples of the 

 truth of the same view. In 

 looking at Coulet's (1. c., figs. 

 2 16,) illustrations of the 

 separate joints (Proglottides] 

 of a Tcenia solium in their 

 various states of contraction 

 and expansion, (fig. 22,) it is 

 impossible not to admit the 

 conception that these animal 

 bodies are independent exist- 

 ences. The separate joints (that is, the Proglottides^ of the 

 other species of Tcenia are perfectly similar to these; and the 

 Proglottides described by Van Beneden in the cestoid genera 

 Echeneibothrium, Phyllobothrium, Ant hobo thrium, Acanthobothrium, 

 Onchobothrium, Calliobothrium, and Tetrarhynchus, (all charac- 

 terised by clearly marked articulations), closely resemble them. 



Since we must henceforward regard these Cestoidea as com- 

 pound animals, we may compare the many-jointed tape-worm 

 with a polypidom, although we must not forget that there are 

 some points of difference between the two. In the compound 

 polypes, the individuals bud out in various directions and relative 

 positions from their parent stock, whereby the polypidom, accord- 

 Fig. 22. Single and separated sexually mature joints of T&nia solium (of the natural 

 size) with lateral sexual apertures, (*) and in different states of expansion and contrac- 

 tion (after Coulet). Each of these separate joints must be regarded as a sexual indi- 

 vidual of the Tcenia solium, and is the proglottis of this Cestoid worm. 



1 ' Versuch einer naturgemasseu Eintheilung der Helminthen,' 1827, p. 21. 



2 ' Les Vers Cestoides,' 1850. It is to he regretted that Van Beneden has confined his 

 investigations to the scolices and proglottides, and has not examined the development of 

 the embrvos. 



