592 SUMMARY OF CURRENT RESEARCHES RELATING TO 



they seem to do good service by their destruction of organic matter, while 

 their faeces increase the goodness of the mud. Their power of regeneration 

 is very remarkable. 



Mr. "W. B. Benham * has made this worm the subject of the third of 

 his " Studies on Earthworms." The epidermis has but few mucous cells, 

 and between its cells there pass blood-vessels as in the leech, Perionyx, 

 and PericJieeta. A considerable difference in appearance was detected 

 behind somite XY. and extends to about somite XLVII., and the epidermis 

 is there changed in character ; in addition to the columnar cells of the 

 general surface, there is a layer of elongated club-shaped cells, which 

 have a very similar aj)pearance to those in the clitellum of Lumhricus and 

 Microchseta ; another point of difference from Lumh-icus is the absence of 

 strands of connective tissue separating the club-shaped cells into more or 

 less distinct groups. This clitellar structure appears to have been over- 

 looked from its commencing and ending gradually, and from there being 

 no difference of colour in the living worm. The nephridia-pores were 

 not detected. From all other earthworms save Pontodrilus, Criodrilus differs 

 in the absence of a gizzard ; there is a moderate-sized typhlosole, contrary 

 to the statement of Vejdovsky. The nephridia are not present in front of 

 somite XIII. ; in and behind it they are large organs, with a slight 

 muscular vesicular portion. The seminal reservoirs are constructed on the 

 plan of AUolohopJiora ; the testes have a digitate form, and from their deep 

 position are very difficult to find at first. The ovary is a flattened rounded 

 disc, and the receptaculum ovorum, or, as Mr. Benham prefers to call it, 

 the ovisac, is a botryoidal protrusion of the posterior septum of somite 

 Xm. The author thinks that Dr. Oerley is mistaken as to the spermathecae, 

 as he was unable to find any trace of them, and it is suggested that the 

 ciliated rosettes were mistaken for them. The worm should be looked for 

 in this country. 



Sig. D. Eosa sums up j the principal facts observed in his researches on 

 Criodrilus lacuum, especially those relating to the genital organs, of which 

 he enumerates the parts and indicates the position relative to the segments. 



From his researches the author arrives at the following conclusion : 

 " Criodrilus has its nearest relations in the AUolobophora (J., turgida 

 Eisen, &c.) ; it belongs to the same phylum of the true Lumhricidse, of which 

 it is an extremely modified form." 



He proposes to create a sub-family Criodrilinse of the family Lum- 

 hricidse. 



Anatomy of Priapulidas. J — Dr. H. Schauinsland has continued § his 

 studies on Halicryptiis and Priapulus. The central nervous system lies 

 altogether in the ectodermal epithelium. Although it is not in any way 

 distinctly segmented, yet there are indications of segmentation. In the 

 regular interspaces which lie between the separate bundles of circular 

 muscles, there is a greater aggregation of ganglionic cells than in the rest 

 of the course. Just in front uf the division of the oesophageal ring there are 

 three ganglionic masses, which correspond to the suboesophageal ganglion of 

 Annelids. Peripheral nerves are given off from the sides of the nerve-cord 

 aloDg its whole course, a larger number being, of course, given off from the 

 ganglionic swellings than from elsewhere. This intensifies the impression 

 of a commencing metamerism of the nervous system. The peripheral nerves 

 never form a completely closed ring, as they are said to do in Sipuncnlus, 



* Tom. cit., pp. 561-72 (11 figs.). 



t Boll. Mus. Zool. e Anat. Coiup. E. Univ. Torino, i. (1886) pt. 1.5. 



J Zool. Anzeig., x. (1887) pp, 171-3. § See this Journal, ante, p. 91. 



