SOME POINTS IN THE ANATOMY OF POLYCH.ETA. 259 



ova and spermatozoa by dehiscence, and they invariably died 

 after being kept some time. Sections revealed no ova or 

 spermatozoa in the nephridia, in fact it seems impossible that 

 the ova should be found in the lumen of the nephridium, for 

 the ovum is many times larger than the tube of the latter in 

 diameter, being nearly equal in size to the whole body of the 

 nephridium. 



2. The " Cardiac Body." 



Dr. R. Horst, of Leyden, in ' Zool. Anz.,' viii, published a 

 discussiou of this curious and problematic structure. He gave 

 an account of his own examination of the heart in some speci- 

 mens of the genus Brada, belonging to the family Chlorhse- 

 midse, and from the structure of the cardiac body in that 

 genus, and a comparison of it with certain structures in the 

 Oligochseta, draws the conclusion that the cardiac body in 

 Polychseta is originally derived in the embryo from the intes- 

 tinal epithelium, is, in fact, an evagiuation from the intestine. 

 Dr. Horst gives a rapid sketch of the history of our knowledge 

 of the heart in the Chlorhajmidae. The organ was first men- 

 tioned by Otto in 1821, 1 and considered by him to be a second 

 oesophagus. Claparede gives an erroneous description of the 

 organ ('Ann. Chet. de Naples ') ; he says it is a tubular structure, 

 which appears to open anteriorly in the dorsal wall of the buccal 

 cavity. Delle Chiaje also considered the heart to be con- 

 nected with the digestive system. Gab. Costa, Dujardin, 

 Max Miiller, and Quatrefages have all recognised the organ 

 as a true heart, whose function is to propel the blood into the 

 branchiae. Claparede, however, seems to have been the first to 

 discover the curious dark-coloured cells containing granules, 

 which occur in the heart, while those zoologists who recognised 

 the true function of the heart were unaware of anything pecu- 

 liar in its structure. Claparede met with the cells of the car- 

 diac body, and thought the organ was entirely glandular, while 



1 "De Sternaspide et Siphostomate," 'Nova Acta Acad. Caes. Leopold 

 Nat. Cur.,' x, pars 2. 



