802 SUMMARY OF CURRENT RESEARCHES RELATING TO 



with the buccal rings of the Snatangida). He is of opinion that tho 

 circulatory systoni of both regular and irregular Echinoids is funda- 

 mentally similar ; that there are not two systems absolutely distinct 

 from one another, since in the regular forms the two peri-oosophagcal 

 rings are either connected by anastomoses, or by the branches which 

 each of them sends into the Polian vesicles, and since in the irregular 

 there is a disappearance of part of tho sand-canal. The sand-canal 

 and the glandular canal of Echinus is represented in Spatangus by 

 tho structure for which he retains tho name of sand-canal, although 

 he recognizes that it is formed of two vessels. 



Hamann's Researches on the Echinoidea.*— Prof. P. Martin 

 Duncan has satisfied himself that the " globifera " of Hamann arc 

 glandular organs and distinct from tho pedicellariflc globifera; of 

 Sphaerechinus. He points out that the glandular globes are more 

 united at their common base than Hamann's diagram would indicate ; 

 that their function is partly the same as that of the similarly named 

 pedicellariae, and he suggests that they are modified pedicellariae. 



Vascular System of Dorocidaris papillata.f — M. H. Prouho states 

 that in Dorocidaris papillata the sand-canal opens directly into tho 

 madreporic plate, together with another duct, and into a single orifice 

 towards which all the aquiferous pores converge. The so-called blood- 

 vascular system has its ring communicating with the intestinal absorb- 

 ent vessels by the oesophageal branch of the internal marginal vessel. 

 The ring also gives rise to a vascular plexus which is distributed over 

 the ovoid gland, and is continued into the mesenteric layer, which unites 

 the five central glands. The ring also gives rise to five pharyngeal 

 vessels, the existence of which has been denied by preceding French 

 authors. The blood- and water-vascular systems are intimately con- 

 nected by means of their respective rings. The author does not 

 agree with Prof. Perrier in thinking that Echinoids have only one 

 vascular system ; nor can he agree with those who think that the two 

 systems are entirely distinct. The cavity of the ovoid gland is con- 

 tinuous with that of the duct which opens beside the sand-canal. 

 This duct has nothing to do with the blood-vascular system, and the 

 gland itself appears to be the seat of production of the flagellate cells 

 which are so abundant in the perivisceral cavity. 



Functions of Ovoid Gland, Tiedemann's Bodies, and Polian 

 Vesicles of Asterida.J — M. Cuenot finds that the ovoid gland, the 

 bodies of Tiedemann, and the Polian vesicles have one and the same 

 function. They form the pigmented corpuscles which float in the 

 liquid of the vessels and of the general cavity. Their histological con- 

 stitution is the same, being made up as it is of connective fibres sup- 

 porting pigmented cells. The ovoid gland is closed, while the bodies 

 of Tiedemann and the Polian vesicles open into the oral ambulacral 

 ring. The author states that at certain times the gland allows its 

 desquamated cells to escape into the body-cavity. If a specimen is 



* Ann. and Mag. Nat. Hist., xviii. (1886) pp. 66-9. 



t Comptes Rendus, cii. (1886) pp. 1403-6. J Ibid., pp. 1568-9. 



