466 Miscellaneous. 



On the Organization and Development of the Gordii. — Second Note*. 

 By M. A. Villot. 



In the Gordii the adult state is characterized by the atrophy of the 

 digestive apparatus, and the development of the generative organs, 

 the integuments, the muscular apparatus, and the nervous system. 



The integuments have not the complex structure that Dr. 0. von 

 Linstow has recently attributed to them. "We can only distinguish 

 in them two layers — a superficial structureless layer scarcely measur- 

 ing 0-OUl millim., and a deeper one, formed of intercrossed elastic 

 fibres, more or less strongly coloured, and having an average thick- 

 ness of 0*029 millim. These two layers correspond to the cuticle 

 of the Nematoids, and do not differ from it in origin. The elastic 

 fibres which constitute the deep layer are only differentiated to- 

 wards the close of the second larval period. 



The description that I have given of the nervous system is very 

 naturally explained by organogeny, and is not without analogy 

 to that which is accepted for other animals. The relations of 

 continuity which exist between the cerebroid organ, the ventral 

 cord, and the hypoderm are shown by longitudinal and transverse 

 sections. These are facts which I have been the first to indicate, 

 and which possess a certain value, independently of any physiolo- 

 gical interpretation. In the larva of Gordius we find, in place of 

 the cerebroid organ, an actual ring which gives passage to the oeso- 

 phagus, and is the homologue of that which is observed in all 

 Nematoids. The transformation of the oesophageal collar into a 

 cephalic ganglion in the adult Gordii is the consequence of the dis- 

 appearance of the oesophagus. The union of the medullary centres 

 into a single cord situated in the ventral region is the result of the 

 fact of the non-existence in the Gordii of lateral areas, submedian 

 lines, or dorsal line. This important character fully justifies the crea- 

 tion of a special order for the genus Gordius ; it approximates these 

 animals to the Sipunculi, and in this way establishes a well-marked 

 passage from the class of Helminthes to that of the Gephyrea. The 

 network of fibres and cells which constitutes the hypoderm is placed 

 beyond doubt by means of suitably directed sections and the em- 

 ployment of colouring-matter ; and its ascription to the nervous 

 system has nothing startling in it when we consider the transitory 

 forms which this apparatus assumes among the superior types of the 

 animal kingdom. The nervous system of the Gordii is arrested at 

 that phase of development which represents the differentiation of 

 the medullary centres by gemmation from the ectodermic lamella. 

 Although still intimately united with the hypoderm, their ventral 

 cord has already passed the muscular zone and penetrated into the 

 middle region of the body. It is the same organogenic phase that 

 we observe in the adult Nematoids ; but here the differentiation of the 

 nervous centres appears to be less advanced. It is still less so in 

 the Polygordians. Polygordius Villoti has a ventral cord of very 

 flattened form, situated beneath the muscular layer and in imrue- 



* See ' Annals,' August 1880, p. 169. 



