868 Zoological Classification. 



will be understood by those who perused a recent article which 

 we published, founded on Dr. Cobbold's magnificent work.* 

 The first group of Professor Huxley's Scolecida is formed of 

 the Botifers, several of which have been described in our former 

 number. Then follows the Turbellaria, the Trematoda, or 

 Flukes, concerning which our subscribers will find much in 

 papers by Dr. Cobbold t which we have already laid before 

 them : and we may make the same remark concerning the 

 Taaniadae, or tapeworms, while the Neniatoidea, or round-worms, 

 and the Acanthocephala and the Grordiacia have been alluded to 

 in a number already cited. The first four of these groups 

 exhibit the water-vascular system in a striking way; and 

 Professor Huxley says, "In none of these animals has any 

 other set of vessels than those which appertain to the water- 

 vascular system (if I am right in my view of the vessels of the 

 Nemertidse) been observed, nor has any trace of a true heart 

 been noticed. - " The nervous system consists of one or two 

 closely approximated ganglia. Professor Huxley considers 

 that the Botifera, the Turbellaria, Trematoda, andTasniada, must 

 be placed in one great assemblage; and that if certain vessels 

 seen in the nematoid worms are homologous with the water 

 vessels of the Trematoda, they must be added to the group, 

 with a probability of carrying with them the Grordiacea and the 

 Acantho cephala . 



The value of this arrangement will depend upon the 

 opinion that is finally formed concerning the importance of the 

 water-vascular system, as affording a sufficient characteristic 

 for associating together animals so different as a rotifer, with 

 an elaborate digestive apparatus, including a very remarkable 

 masticatory apparatus, and a tapeworm, which has no mouth 

 and no digestive 'canal. The tapeworms likewise exhibit the 

 phenomena of alternate generation, the union of the sexes in 

 the same individual in its perfect form ; while the rotifers have 

 no alternate generation, no sexless condition, and exhibit male 

 and female organs in distinct individuals. 



Professor Huxley confesses that the division provisionally 

 termed Scolecida is in an unsatisfactory state, and. it seems to 

 us that farther researches into the nature of the contractile 

 vesicle and canals of the Paramecia and other ciliated infusoria 

 are necessary before the value of the water- vascular system as 

 a ground of classification can be decided upon. 



The Annelida, comprehending the leech, earthworm, lob- 

 worm, sea mouse, etc., all possess a nervous system, which 

 consists of a longitudinal series of ganglia, situated along one 

 side of the body ; " but no annelid ever possesses a heart com- 



* No. xxxiii., p. 190. 



t Vol. i, pp. 2, 115, 347 ; vol. ii., p. 82 ; vol. iii. p. 86 ; vol. iv., p. 390. 



