956 SUMMARY OF CURRENT RESEARCHES RELATING TO 



with vitelline granulations corresponds therefore to a meso-endoblast, from 

 which the future mesoblast cells are the first to be differentiated. 



Organization of Chsetopterus.* — M. J. Joyeux-Laffuie has examined 

 Chsetopterus Valencinii. He finds that the median hinder groove does not 

 stop at the level of the first pair of appendages of the median region, or 

 continue on to the second, as various authors have stated, but that it 

 bifurcates and goes on as two deep grooves ; their function is to conduct to 

 the oral infundibulum the food-particles brought by the current of water 

 which passes through the tube of the worm, and they are therefore analogous 

 to the endostyle of Ascidians, 



The nephridia are remarkably developed in Chsetopferus, but they are 

 not found in the most anterior division of the body. The infundibulum is 

 semilunar, and the whole of its internal surface is covered uniformly with 

 long vibratile cilia. At the level of each appendage the tube is enlarged 

 to form a pouch, which is of considerable size, and opens to the exterior by 

 a short canal. The cilia on the lining epithelium are very well developed. 

 The tissue of the walls of the nephridium is formed of elements which 

 resemble the cells of the organ of Bojanus ; when separated they are 

 spherical in form, and they contain a large nucleus which has one or more 

 concretions in its interior ; they sometimes increase in size and unite, 

 when they form a calculus which almost completely fills the cell. Free 

 calculi are often found in the excretory canal or in the pouch, and then the 

 cells which give rise to them disappear. 



The sexes are separate, but the male and female gonads have the same 

 form and position ; the products accumulate in large quantities, and give to 

 the male a pale white, and to the female a slightly rosy colour. 



Histology of Eunice.! — Prof. E. Jourdan describes the histology of 

 two species of the genus Eunice — E. Harassii and E. torquata. The cuticle 

 is remarkable for its thickness, and is seen by the use of reagents to consist 

 of superposed lamellae, which sometimes give it a regularly striated appear- 

 ance ; the existence of pores is best demonstrated after the use of such 

 reagents — e. g. Hoffmann's green — as colour the contents of the underlying 

 glandular cells. The epidermis is formed of cylindrical epithelial elements 

 and glandular cells ; the former are connected with one another by basal 

 anastomosing branches, and give rise to the arrangement which Claparede 

 distinguished as stellar connective tissue. The glandular cells are irregu- 

 larly disposed on the body, being very rare on the dorsal surface, and most 

 common at the edges of the ventral ; some of these cells are hyaline and 

 some are granular in appearance, but both are modifications of a single 

 type of anatomical element. When the muscular fibres are teased, the 

 irregularity and often the bizarre appearance of their forms are the first 

 point to attract attention ; they seem to be very long, are irregularly 

 flattened, and indicate waves of contraction by thickenings scattered very 

 irregularly along their whole extent. The author thinks that he has found 

 evidence of true nerve-endings in the muscles, and states that he has 

 observed similar arrangements in Holothurians. 



In the account of the central nervous system we must content ourselves 

 with noting a few points : the dotted substance is composed of very deli- 

 cate, homogeneous fibrils quite like those which are met with in the peri- 

 pheral nerves ; they form so inextricable a plexus that the dotted substance 

 cannot be separated out ; the spaces of the close and delicate plexuses are 

 occupied by an interfibrillar protoplasm which is sufficient to convert the 



* Comptes Rendus, cv. (1887) pp. 125-7. 



t Ann. Sci. Nat.— ZooL, li. (1887) pp. 239-304 (5 pis.). 



