656 SUMMARY OF CURRENT RESEARCHES RELATING TO 



elements are larger than in other Oligoclifeta ; in transverse sections 

 one may observe a distinct striation, and in surface views a system of 

 intercrossing bands, formed of fibres. The setal follicles are provided 

 with large orifices which are set in the long axis of the body, and, in 

 addition to these, there are the openings (macropores) of the canals 

 of the dermal glands, and a large number of " micropores." Similar 

 observations on the structure of the annelid cuticle have been made, 

 and will shortly be published by Voigt, who has especially busied 

 himself with Brnncliiohdella. After describing the setfe, the author 

 passes to the epidermis, and then to the musculature, the different 

 parts of which are fully described. The blood-vascular system is 

 stated to have the closest relation to the intestine, and the account of 

 Leydig is, on the whole, confirmed. 



The nervous system displays, from the third segment backwards, 

 the arrangement of a double ganglionic swelling in each segment ; 

 these two parts are connected together by the ordinary oesophageal 

 commissures. Notwithstanding their distinct sejiaration, these double 

 ganglia must be regarded as the enlargements of a single ganglion, 

 inasmuch as the investment of ganglionic cells is not broken in the 

 intermediate space, although it is reduced in the longitudinal com- 

 missure which traverses the dissepiment to a median and ventral row 

 of cells ; and, further, the number and distribution of the primary 

 nerve-branches in each segment of Phreoryctes correspond to the 

 relations found in other Oligochfeta. After describing the general 

 distribution of the nerve-trunks, the author points out that the nervous 

 connection with the epidermis is distinguished by a distinctly dotted 

 striation, such as is characteristic of fine nerve-fibrils. In the head 

 the elements of the nervous system are of considerable size. 



The well-developed septa consist of two membranes of connective 

 tissue, which are separated off from the general peritoneum which 

 covers the longitudinal system of muscles ; owing to the great deve- 

 loj)ment of the fat-bodies in the neighbourhood of the segmental 

 organs, the perivisceral fluid occupies a jiroportionately small space. 



By the aid of high powers, Timm was led to think that the cuticle 

 of Nais was characterized by the presence of a number of extremely 

 fine holes, but he was not able to absolutely convince himself of this. 

 Among the remarkable forms of setfe in this genus the author detected 

 one which, as he thinks, has not been yet described, and the species 

 in which it is found being apparently new, their form justifies the 

 application of the specific term hamata. 



The ventral medulla is not so distinctly segmented as in the other 

 Oligochseta, a fact which is probably to be explained by the rich 

 develoj)ment of the cells on the ventral surface, for these frequently 

 cover the whole of the under side of the longitudinal commissures. 

 The author confirms the observation of Semper that, at the end of the 

 body, the ventral medulla (at least in all asexual forms) passes 

 directly into the epidermis. The suiira-oesoiihageal ganglion consists 

 of two fairly separated halves, the gangliouic investment of which 

 passes directly into the layer of cells which invests the caecum con- 

 nected with the oesophagus. 



