History of the Hairy-bached Animalcules. 391 



tonotus and Turbanella the skin is not melting, but capable of 

 resisting, to some extent, cold potass solntion. It is ciliated 

 only on the ventral surface, and, in the former genus, only on 

 a portion even of this. The ring of cilia which surrounds the 

 head of Turbanella, and the muscular coat of the alimentary 

 canal of the Ohgetonotes generally, sharply defined against the 

 parenchyme of the body, especially in the anterior third, are 

 conditions unknown among the Turbellaria ; while the motory 

 muscles, nerve-threads, and water-vessels common to them, 

 have not been recognized in those. Yet Dr. Schulze judges 

 that a certain relationship between the Ohcetonotidce and the 

 Tuebellaeia is not to be mistaken : 1, because of their inarti- 

 culate body, in- size and form resembling the little Vortex- 

 worms ; 2, because of the absence of any other locomotive 

 organs than skin-cilia, by means of which, though covering only 

 one half of the body, the animals yet proceed with a soft gliding 

 motion, like that of the Yortex-worms ; 3, because the absence 

 of muscles, nerves, and vessels is approached by the obscure 

 condition and receding development of these organs in many of 

 the more minute Rhabdocoela and Microstomata. Thus there 

 seems here a closer affinity than with the Annelida. 



Difficulties, however, beset the attempt to assign to the 

 Ohcetonotidce their natural place in the class Tuebellaeia. The 

 Bendroccela and the Rhyncoccela are at once excluded; the 

 former consisting of animals of superior size, furnished with a 

 ramified intestine without an anal orifice ; the latter having, in- 

 deed, a straight intestine, provided with an anus, but invariably 

 possessing a protrusile proboscis. There remain the Rhabdo- 

 coela and the Arhynchia.* Both these groups contain small 

 forms, resembling those of the Ohcetonotidce ; but the former 

 have an intestine without an anus, and a hermaphodite system 

 of reproduction ; the latter an anal orifice, but a dioecious re- 

 production. Thus the Chaitonotidce, hermaphrodite and fur- 

 nished with an anus, cannot, without force, be referred to 

 either. 



In the Tuebellaeia, as in the Veemes generally, those cha- 

 racters which are drawn from the form of the alimentary 

 canal have a higher systematic signification than such as depend 

 on the condition of the reproductive system. If the Ohcetono- 

 tidce, then, are to be placed among the Tuebellaeia, Dr. Schulze 

 would associate them, not with the Rhabdocoela, but with the 

 Arhynchia ; which would include the Microstomata and Dino- 

 philus as dioecious, the Ohcetonotidce as monoecious forms. 



Finally, this able zoologist, taking into consideration all the 

 facts recorded, considers it premature to determine the actual 



* Vide Schulze' a JBeitr. z. Naturg. d, Turbellarien. 



