290 NOTES AND MEMORANDA. 



predecessor in bis office, Dr. Murie, in two quite distinct species of 

 Khinoceros.* 



Researclies on Bonellia viridis. — This interesting Gepliyrean 

 genus has been studied by F. Vejdovsky, who gives an account of the 

 mode of formation of the eggs in the female, and of the organization 

 of the male.f 



1. Formation of the Ova. — The ovary is attached to a sort of peri- 

 toneal fold, and at its least developed end shows small accumulations 

 of similar cells. Of these ova one, enlarging at the expense of the others, 

 becomes the egg-cell ; the sister-cells, or follicular cells, being gradually 

 compressed and flattened until they form a mere secondary membrane 

 to the egg, external to the vitelline membrane. Some of the sister- 

 cells, however, do not take on the character of a follicular epithelium, 

 but form a hollow cap over one pole of the egg, outside the follicle ; 

 these also gradually dwindle away as their substance is absorbed by the 

 rapidly developing egg-cell, until finally they vanish altogether. 



2. Structure of the Male. — The curious parasitic Turbellarium- 

 like male of Bonellia, discovered by Kowalewsky, was found by Vej- 

 dovsky in the oesophagus of young females, as well as in the oviduct 

 of sexually perfect females, and in the mud in which these live. It 

 is a minute elongated creature, covered with a ciliated cuticle, and 

 having a straight, widish alimentary canal opening by a mouth near the 

 anterior end of the body, and contained in a body cavity ; there is also 

 an indistinct non-ganglionated ventral nerve-cord. The spermatozoa 

 are formed from cells detached, as rounded aggregations, like those 

 from which the eggs are produced, from the peritoneal membrane lining 

 the body cavity. The spermatozoa pass by a ciliated funnel into 

 a spacious vesicula seminalis, which lies on the dorsal side of the ali- 

 mentary canal, and opens by an aperture at the anterior end of the 

 body. The male excretory apparatus thus closely resembles that of 

 the female, in which there is a ciliated funnel leading by a duct into 

 a uterus in which the eggs are stored, and which oj^ens externally by 

 an oviduct. In both sexes, also, there is a pair of chitinous hooks in 

 relation with the genital aperture : these were discovered in the male 

 by Marion, who contributes a woodcut illustrating their position to 

 Vejdovsky's paper, which is further accompanied by a plate. 



The male of Bonellia is alsi > treated of in a short paper by Selenka,;}: 

 whose account differs in certain important respects from that given 

 above. He denies the presence of a cuticle, and states that the external 

 layer of the body is covered by ordinary ciliated cells. He denies 

 also the presence of both mouth and anus, and describes the nervous 

 system as possessing a distinct suboesophagcal ganglion and circum- 

 oesophageal ring. The animal also possesses, according to Selenka, a 

 pair of segmental organs in the hinder third of the body. He remarks, 

 in conclusion, upon the intei'est oi Bonellia as affording one of the few 

 cases of polyandry known in the animal kingdom ; four to twelve or 

 even twenty males being found in a single female. 



* 'Proc. Zool. Soc.,' Nov. 1877. 



t ' Zeitschr. f. wiss. Zool.,' xsx. (1879) 487. 



i ' Zool. Anzeiger,' i. (1878) 120. 



