248 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is also made up by a short and narrow canal, which lies in the wall of 

 the anal tube, to the long axis of which it runs parallel, and into which 

 it finally opens. The canal is lined by a ciliated epithelium. Of the 

 numerous infundibula on the surface one deserves especial mention ; 

 it is the one which lies at the tip, is larger, and is, no doubt, morpho- 

 logically the primary infundibulum. When we come to consider the 

 exact character of these tubes, which have been by all observers 

 regarded as appendages of the enteron, we are met by the difficulty of 

 having to define what is the true end of that tract ; they open behind 

 the sphincter-like thickening of the circular musculature of the hind- 

 gut, and between it and that anal portion which is so well provided with 

 glands. This last would seem to be a portion of the outer skin, and 

 if it be so it is probable that the " anal tubes " have morphologically 

 no relation to the true enteron ; but this is a point which can only be 

 decided by further investigations, and esiiecially by those undertaken 

 from the embryological side. 



It will be seen that these results are very far from being in 

 accordance with those of Greef;* and Dr. Spengel proceeds to 

 point out what he believes to be the misleading influences in Greef s 

 experiments. 



The vascular system is very simple, consisting merely of a ventral 

 and of a dorsal vessel, with two connecting loops. The contained 

 fluid is colourless and the corpuscles are amoebiform, with long sharp 

 l)seudopodia, or are stellate. Similar cells are found in the coelom, 

 but no connection between the two systems of cavities could be made 

 out. 



The spoon-shaped cephalic lobe is shown to contain a number 

 of hollow spaces, the whole system of which is a continuation 

 forwards of the coelom. After this we come to the segmental 

 organs, of which there are two pairs. The anterior lies behind 

 the anal setje, and the posterior some way further back. In front 

 of their orifice they give off a short, and behind it a longer sac; 

 in their walls we find an internal epithelium, two layers of muscles, 

 and a peritoneal investment. In some cases balls of pigmented cells 

 are to be detected below the epithelium, and it is these aggregations 

 which give rise to the ai:)parent presence of a vascular plexus. These 

 balls would hardly seem to be products of excretion. The cavity of 

 each segmental organ communicates freely with the coelom ; the in- 

 fundibula are provided with membranous valves ; by the segmental 

 organs, the product of the last set of organs to be described, escape to 

 the exterior. These are the generative organs, the characters of which 

 are very indifferent, so that it is safer to call them germ glands than 

 to distinguish them as testis or ovary. The gland lies at the hinder 

 end of the body, and gives rise to spheres of cells. In the female 

 there are not, as in Bonellia, any investing cells around the primitive 

 ova. When the groups of cells break oft' from the gland they move 

 freely about in the coelom ; in the male the cells are set free in groups 

 of from thirty to forty, and, unlike the ova, they long remain connected 

 together. The author, in a supplementary note to this long paper, 



* Sec this Joiiiual, iii. (1880) p. 434. 



