ON THE ZOOLOGICAL STATION AT NAPLES. 2o5 



most elaborate network of tubules lying for the most part within the 

 muscular layers of the body wall. Tins network is continuous, the 

 portion lying on the one side of the body with the portion lying on the 

 other side in the median ventral region, and is also continuous throughout 

 the length of the body in the region in which it occurs— i e., from the ninth 

 post-oral ganglion to the nineteenth. 



The tubules collect at certain spots, and pass down to open to the 

 exterior without the intervention of any vesicle. There are 10 pairs of 

 such apertures placed in somites 10-19 inclusive, upon the first annulus 

 of each somite. The apertures are thus metamerically. related to the 

 funnels, a pair of apertures corresponding with each pair of funnels. 



The organ in reality consists of a paired series of nephridia, each with 

 a funnel to the interior, and a pore to the exterior, and these nephridia 

 differ from those in llirudo, Cl&psine, etc., in that they remain continuous, 

 those on the one side with those on the other, and each pair with those 

 in front and behind. 



Supposing, as we are probably justified in doiug, that the organs 

 have arisen by a hollowing of branching mesoblastic cells, we have here 

 a structure which has only advanced upon this primitive condition in 

 developing metamerically repeated funnels and apertures to the exterior. 



I obtained but very few specimens of Branchellion. I was, however, 

 able to demonstrate the existence of a very similar nephridium in that 

 genus, but I believe far simpler, in that it has not developed any internal 

 funnels and has only a single pair of pores to the exterior, these corre- 

 sponding to the most posterior pair in Pontobdella. : 



The commonest Pontobdella at Naples belongs to the species P. 

 mwricata, but I obtained single specimens of perhaps two other species, 

 and a specimen which must probably form a new genus ; but I should 

 wish to become much more fully acquainted with all the varieties at 

 present known before entering upon any toxonomic questions in a group 

 which presents considerable difficulties in this respect, the characters of 

 most value in forming a systematic arrangement— the number of annuli 

 in a somite, etc. — being at present very inaccurately described. 



Since the discovery of Haplob ran elms, a new genus of Capitobran- 

 chiate Annelids belonging to a small, but in many ways very interesting 

 group, I have endeavoured to obtain as many members of the group 

 as possible, in order to complete a comparative study of the group ; this 

 I carried out further at Naples. I obtained species of Oria, Fabricia, and 

 Am/pMglena, and obtained new results with regard to the structure of these 

 forms. ^ I may state here that I have confirmed the observations of 

 Claparede, which have lately been doubted, as to the arrangement of the 

 modified pair of nephridia which serve as tubiparous glands, and the median 

 position of their aperture to the exterior, in Amphiglena. 



At the request of Professor Laukester, I undertook the investigation 

 of certain problems connected with the blood system of Mollusca and the 

 supposed taking in and shedding out of water by these animals. I studied 

 bolen legumen, and entirely corroborated the results previously obtained 

 at Naples by F. G. Penrose, to the effect that ordinary blood does not exist 

 in the pencardinm of that animal, and so probably of other Lamelli- 

 branchs This I demonstrated by means of serial sections which show 

 tne nucleated blood corpuscles lying in the ventricle, but absent from the 

 pericardium. 



With regard to the supposed taking in of water, I kept various forms, 



