!iSS 



SUMMARY OF CXJBRENT RESEARCHES RELATING TO 



Morphology of the Gordiidae.*- Prcf. F. Vejdovsky is of opinion 

 that although the external form of the body appears to ally tlie 

 Gordiidae with the Nematoid worms, the rest of their organization is 

 so different that they ought to be separated from that class of 

 Nematohelminths, and brought into closer relation with the Annulata; 

 the presence of a true coelom and of mesenteries, as well as the highly 

 developed central nervous system, and the segmental arrangement 

 of their glands, demand this change. 



At certain times the so-called cellular tissue may disappear and 

 a coelom clothed by a pavement epithelium developed ; this epi- 

 thelium corresponds to the peritoneum of Annulates; the enteric 

 canal has, however, no enteric fibrous layer, and herein resembles the 

 enterou of Nematodes. This may be explained by the fact that the 

 Gordiidae take in no food during their free-living stages, while the 

 conditions of these parts are unknown in the younger and parasitic 

 stages. As in the Annulata, the mesenteries arise by the differentia- 

 tion of the epithelial layer of the coelom. 



By continuous direct cell-division the so called cellular tissue 

 gets to fill all the spaces of the coelom ; when this is absorbed their 

 plasma is used for the development of the gonads. The elements of 

 the cellular tissue correspond to the lymph-cells of Annulates, which 

 play an important part in their generative activity. 



The relations of the peripharyngeal ganglion are difficult to 

 compare with the nerve-ring of Nematodes, and can be better ex- 

 plained by supposing that there has been a modification of the 

 primitive cerebral ganglicn, pharyngeal commissure, and commence- 

 ment of the ventral cord, owing to the reduction of the pharynx. 

 The histological stiucture of the suprapharyngeal portion recalls 

 that of the cerebral ganglion of Annulates ; the fusion of the com- 

 missures with the ganglia leads to the large peripharyngeal ganglion. 

 Both developmeutally and histologically the ventral cord agrees with 

 that of Annulata, for it arises from two primitive halves, which are 

 themselves formed by the thickening of the epiblast, and it consists 

 of an inferior layer of ganglionic cells and an upper fibrillar layer, 

 among which arc the much- branched processes of the lower ganglionic 

 cells. Although the peripheral system of the Gordiidae is very dif- 

 ferent from that of the Annulata, consisting as it does of a lamella 

 connected with the hypodermis, it is not difficult to find homologies 

 between the two ; and indeed, Phreoryctes has a so-called ventral 

 organ which calls to mind the structure of Gordius. 



The internal segmentation of the Gordiidae is exhibited only by 

 the gonads. Other, less important, resemblances between the group 

 which Dr. Vejdovsky seeks to unite are to be found in the structure 

 of the body-wall, the hypodermis of the Enchytraeidae being exactly 

 like that of the Gordiidae; Polygordius, again, has, like Gordius (and 

 the Nematoids), no circular muscular layer. The structure of the 

 muscular tissue is of the Annulate and not of the Nematoid type. 

 The author proposes to form for the Gordiidae a sejmrate order, which 

 may be called that of the Nematomorpha. 



* Zeitsclir. f. Wiss. Zoul., xliii. (IS8G) pp. 369-433 (2 pis.). 



