ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 247 



observations of Hatschek which would support this view are not in 

 agreement with the description of the development of the ventral 

 medulla of Lumbricus, as given either by Kowalevsky or Kleinenbero-. 

 Nor do Dr. Spengel's own observations on the development of EcUurus 

 or the fact that the canal is continued into the oasophageal commis- 

 sures, support the doctrine of Dr. Hatschek. Only one ganglionic 

 band passes into each of the commissures just mentioned, and in them 

 some of the ganglionic cells lie on the ventral side. Of the anterior 

 peripheral nerves some would appear to be justly called tactile. 



The enteric canal is a good deal complicated. Its two orifices are 

 at either end of the body ; the mouth, which can be closed by a 

 sphincter muscle, leads into a wide pharynx, and at its hinder end 

 there is a diaphragm. This structure calls to mind the dissepiments 

 of the Annelids, and would appear to be of very considerable signifi- 

 - cance as an indication of a division of the body into two segments. 

 The oesophagus which follows the pharynx is succeeded by a very 

 short but wider portion — the crop. The rest of the coiled enteron is 

 several feet long, and appears to be divisible into three portions. In 

 the mid-gut there may be seen on the ventral side a ciliated groove 

 bounded by two epithelial ridges, and a band of longitudinal muscle. 

 Behind the mid-gut the tract is divided into two canals, very different 

 in their diameter, but closely applied to one another along their whole 

 length. The narrow one is never more than 1 mm. in diameter the 

 other varies considerably. The former would be comparable to the 

 secondary gut of the Echinida (Ludwig) and of the Capitellida (Eisig). 

 Where the " hind-gut " joins the rectum, we find the openings of the 

 so-called " anal tubes." To these structures the author passes after 

 an account of the histology of the different regions of the enteron. 

 They are two in number, reddish-brown in colour and varying in 

 size. In young individuals it is possible that their size is continually 

 changing, owing to the great contractility of their walls. This last 

 peculiarity is, also, a very sufficient cause for great misapprehensions 

 as to their true structural characters, and it is always best to study 

 tubes which are found filled with fluid. When carefully examined, 

 each tube is seen to form a greatly elongated non-ramified sac, the 

 walls of which contain three or four layers. The outermost is the 

 peritoneal investment, and it is followed by a muscular stratum divisible 

 into two layers. The constituent fibres cross one another in various 

 directions and form an irregular network ; in sections it is possible to 

 see that two distinct directions are taken by these fibres, for some are 

 circularly and some longitudinally disposed ; the former are the more 

 external. I'he contained epithelial layer has a complicated structure. 

 Broad spindle-shaped groups of cells are to be found between the 

 flattened cells, and the former have extremely delicate, very long 

 cilia. These groups of cells are arranged in pretty regular longi- 

 tudinal lines, and, owing to their pigment, are the cause of the brown 

 coloration of the organ. The surface of each tube is beset with a 

 very large number of small clear corpuscles, in which we may detect 

 infundibular bodies provided with exceedingly long and active cilia. 

 Each of these funnels forms a part of a " ciliated organ," part of which 



