70 SUMMARY OF CURRENT RESEARCHES RELATING TO 



diverticulum of the fore-gut and the " heart " ; it communicates by two 

 trunks with a veutrally running blood-vessel ; above the dorsal blood- 

 vessel is a longitudinal chord of tissue which is the nervous system, 

 and contains several cavities not communicating with each other : in 

 certain species the nerve-cord is he^e oftun coutiuiious with the 

 epidermis by means of delicate cellular strands. Behind the " collar " 

 comes that section of the body which is characterized by the presence 

 of the branchial pouches ; these latter are paired outgrowths of the 

 dorsal wall of the alimentary canal ; each opens by a narrow canal on 

 to a groove which runs to one side of the median line of the dorsal 

 surface of the body ; the internal opening of the canal is guarded by 

 a valve, which does not completely close it, but leaves a permanently 

 open U-shaped space. This simple condition is found in B. Icupfferi 

 and B. Tcovalevshi throughout life. In B. minutus and B. claviger 

 the structure of the branchial pouches is complicated ; the U-shaped 

 cleft is bridged over here and there, and the cavity communicates 

 therefore with the exterior by a series of window-like orifices. The 

 skeletal structures which support the walls of the branchial pouches 

 are described in detail. 



All the species of the genus are of separated sexes. 



The glands are similar in both sexes, and consist of simple or 

 branched tubes ; they are arranged in a series of pairs, and each gland 

 opens separately on to the exterior a little to the outside of the 

 aj^erture of the branchial pouches; they are frequently, however, 

 developed in the region of the body which follows the branchial 

 pouches. 



Echinodermata. 



Process resembling Copulation in Comatula mediterranea.*— 

 C. F. Jiekeli has observed a process in Comatula mediterranea, which, 

 like that described by H. Ludwig in Asterina gihhosa, showed tho 

 closest resemblance to a copulation. 



Two specimens were found one morning close together in the 

 aquarium with the arms entwined. About twelve hours after the 

 discovery of this condition of things, the two individuals were still 

 united ; but on the following morning, or twenty-four hours after the 

 first observation, the union was dissolved. Another still less expected 

 process now commenced. The arms fell off simultaneously with the 

 separation of the pinnules, and broke up into the individual joints. 

 At last only the two oral disks remained. The pinnules, when fished 

 out, were in part filled with semen or covered with adherent ova in the 

 blastula stage, so as to confirm the probable supposition that this 

 entwining of the two individuals might be a process of fertilization. 

 The ova passed through a normal development as far as the penta- 

 crinus stage. The two armless Comatula disks continued for some 

 days to live, and were then killed for histological investigation. 



This observation seems to support Studer's supposition that (at 



♦ Zool. Anzeig., vii. (1884) pp. 448-9. See Ann. and Mag. Nat. Hist., xiv. 

 (1884) pp. 367-8. 



