THE TREMATOD A. 103 



the genus Tetrarhynchis passes through ; but which also 

 in fact includes nearly all Ave know about them ; whilst 

 the great work of Professor Eschricht, upon the genus 

 Bofhriocephaliis of this family, has given an entirely new 

 view of those animals, constituted of almost innumerable 

 joints, so that they are to be regarded according to his 

 anatomical investigations, not as single but as compound 

 animals, \t.z., compound Trematoda omßiikes, so that each 

 joint is to be compared with a distoma, — a view of their 

 nature to which Baer had some time before alluded, and 

 which had also struck Creplin and Mehlis, on account of 

 the resemblance of the sexual organs, but which is now 

 for the first time entitled to the greatest attention, having 

 been rendered probable by so many anatomical researches. 

 However, I cannot for my part entnely coincide in this 

 view of the Cestoid family of worms, for in whatever way 

 the joints and their reciprocal connexion are considered, 

 compound animals are presented, whose construction is 

 entirely different from that of all other animals. The 

 tapeworm is certainly not a single individual, but con- 

 sists of several ; that is, it is constituted of the head, 

 which is an animal, and of the progeny derived from it. 

 This Adew is much supported, it is even proved by the 

 fact, that the offspring ( joints) in a state of progressive 

 development, never actually become animals similar to 

 that from which they spring (the cephalic joint,) which 

 alone remains dissimilar to all the rest, never acquires any 

 developed sexual organs, and consequently never generates 

 any ova, which the others produce in great abundance ; 

 whilst the cephalic joint is furnished with a mouth and 

 suctorial acetabula, proceeds from an egg, and is the 

 animal upon which the development of all the rest de- 

 pends, and is thus in fact one of those anhnals to which 

 we have in the preceding pages given the name of " nurse." 



the thorax and around the heart, and which in Ms opinion were on their 

 migration to the exterior of the animal, (might they not rather be on their 

 migi-atiou to tlie hitestinal canal 'within ?) Eor the rest, I must lament that 

 other occupations prevented my avaüiug myself of the opportunity which 

 wa.s affordcfi mc of making more accurate researches iulo the development of 

 tlic Tdmrhynchi. 



