NEMATODA DESMOSCOLECIDAE 



59 



the dorsal middle line. The locomotor projections are hooked, 

 and are much finer than those of Chaetosoma, and they are 

 situated farther forward than in the last-named 

 genus. Rhabdogaster occurs in the same 

 surroundings as Chaetosoma. Ch. ophicephalum 

 is recorded from the English Channel. 



(ii.) Desmoscolecidae. The members of 

 this family are minute, and are characterised 

 by the presence of well - marked ridges 

 which surround the body and give it 

 an appearance of segmentation. The head, 

 which is somewhat swollen, bears four bristles, 

 and single pairs are borne by a certain num- 

 ber of the ridges, some on the dorsal and 

 some on the ventral surface. These hairs can 

 be moved independently of one another. Two 

 red eye-spots are described between the fourth 

 and fifth rings. The sexes are distinct, and 

 the internal organs generally have a marked 

 resemblance to those of the true Nematoda. 

 The Desmoscolecidae move by looping their 

 bodies after the manner of the Geometrid 

 caterpillars, as well as by creeping with their 

 bristles. The genus contains numerous species 1 : 

 D. minutus Clap. (English Channel), D. nema- 

 toides Greef, D. adelphus Greef, D. chaetogaster 

 Greef, D. elongatus Panceri, and D. lanuginosa FIG. 81. Female Des- 



^ . , 1-1 moscolex elongatus 



Panceri. They are exclusively marine. Panceri, ventral 



Trichoderma oxycaudatum Greef 2 is a view, x 260. a, Ovary. 



, A ' , , . , , (From Pauceri.) 



minute animal, 0'3 mm. long, which has no 

 head or ventral spines, but whose body is ringed and covered with 

 long hair-like bristles. The male has two spicules, and the internal 

 organisation recalls that of other Nematodes ; still its ringed body 

 has induced, some authorities to place it near to Desmoscolex. 



The Life-History of Nematodes. 



Although, considering the enormous number of species of 

 Nematodes and the remarkable diversity of the conditions under 

 1 Panceri, Atti Ace. Napoli, vii. 1878, No. 10. 2 Arch. Ncuurg. 85 (L), 1869, p. 112. 



