ZOOLOGY 



internally in a flame-oell. The nervous sj'stem consists of a large dorsally and 

 anteriorly situated cerebral ganglion or brain giving off a pair of ventro-lateral 

 longitudinal nerves. The sexes are united, and there is no metamorphosis. 



retr 



Fig. 272.— Chaetonotus maximus. 



Highly magnified. (After Zelinka.) 



Fig. 278.— Chaetonotus maximus (or- 

 ganisation), brn. brain ; gld. adhesive 

 gland ; mes. mesenteron ; mo. mouth ; 

 aa, oesophagus ; ov, ovum ; ovar. ovary ; 

 vHr, retractor muscles ; vent, mus, ventral 

 muscle. (After Zelinka.) 



APPENDIX TO THE TROCHELMINTHES- 



The Dinophilea and Hislriobdellea. 



These are two isolated groups of minute animals which may most conveniently 

 be dealt with in association with the Troohelminthes, since they bear cei'tain 

 striking resemblances, now to one, now to another, member of that phylum ; 

 but they differ from all of them in the assumption of a simple kind of meta- 

 merism (p. 43), by virtue of which they have claims to association with the 



