348 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tentacular canals, and tlie system of ambulacral pieces. These canals 

 also present a mode of partition which, is remarkably like what is 

 found in the brachial cavity of the Comatulas ; this mode is alone 

 found somewhat late in the Crinoids, and we see that there is, there- 

 fore, in them "an accidental character" which contrasts strongly with 

 the almost absolute fixity of the relations of the ambulacral appa- 

 ratus. " This last is the essential and dominant character in the 

 organization of an Echinoderm." The authors also find that the 

 integument of the infrabrachial canals is formed of small bipolar 

 cells, the swollen portions of which are near the external surface. 



Genital Passages of Asterias.* — S. Jourdain describes the pre- 

 sence of five vasculiform ducts, lying below and applied to the 

 internal face of the dorsal integument, the sides of which form a 

 pentagon. The angles of the pentagon point to the interradial septa, 

 and a vessel, embracing each septum, establishes a continuity between 

 the branches which correspond to the sides of the pentagon. This 

 vasculiform pentagon was regarded by Tiedemann as a dorsal venous 

 circle, but from each septum there are given off two branches which 

 become connected with the appended genital glands, and they are the 

 only ones which are given off from it. The author is of opinion that 

 this pentagon has no relation to the proper vascular system. The 

 vessels do not have the relations of blood-vessels, but they are in 

 communication with the interior of the gland and its diverticula ; in 

 other words, they are disposed as the excretory canals. The vasculi- 

 form dorsal plexus varies in size with the activity of the genital 

 glands, and its walls are provided with muscles, while the internal 

 ciliated surface has a projecting fold of glandular tissue. At the 

 point of attachment of the enlarged interradial septum, which corre- 

 sponds to the madreporic plate, the ducts of the pentagon open into an 

 elongated fusiform sac, which is invested in an elastic membrane 

 containing muscular fibres. At the extremity of this sac there are two 

 brownish pyriform bodies, which are in connection with the canals of 

 the pentagon ; these, with the sac and its projection, are what most 

 writers have considered to be the heart. They are not so, but merely 

 dilated continuations of the pentagon. The fusiform sac opens into 

 a circum-oral ring, to which are attached small paired globular bodies, 

 almost similar in histological structure to the pyriform bodies. An 

 orifice, of extremely small size, and very difficult to detect, is to be 

 found where the sac is continuous with the circum-oral ring ; so that, 

 Asterias, just as in Holothurians, the sperm and the ova are passed to 

 the exterior by a pore in the circum-oral circlet, and not by interradial 

 perforated plates. 



E. Perrier and J. Poirier state,f however, that specimens of 

 Asterias glacialis, alive and depositing ova, are seen to have their ova 

 escaping by ten groups of small holes, set a little above each inter- 

 radial angle ; each group contains three to six orifices ; in specimens 

 that had been opened from the dorsal surface no ova were to be found 



* Comptes Rendus, xciv. (1882) pp. 744-6. 

 t Ibid., pp. 891-2. 



