424 NATURAL SCIENCE. Dec, 



The author starts from the histological structure of the vessels ; 

 he treats first of the chief trunk, namely, the dorsal vessel, which 

 is often paired, and thus retains the embryonic character ; next of 

 the supra-intestinal vessel, the ventral vessel, the subintestinal and 

 subneural vessels, and last describes the peripheral circulation with the 

 epidermis-capillaries. Only a few forms possess special respiratory 

 organs, such as Dero, Alma, Chetobranchus, Bmnchiuni, and Hesperodrilus. 



The Oligochaeta are all hermaphrodite, and their sexual organs 

 are formed on one and the same plan. The elements present are : 

 (i) the ovaries and testicles; (2) the generative passages, oviduct, 

 and sperm-duct, with egg- and sperm-sacs ; (3) the spermathecae and 

 penial setae. The position of these varies greatly, but they are always 

 metamerically arranged. Except in Aeolosoina the gonads are every- 

 where paired, the ovaries being present usually in one pair (seldom 

 two), and always situated behind the spermaries. The lower 

 Oligochaeta, described by Claparede as " Limicolae," produce large 

 eggs provided with abundant yolk, while the earthworms possess 

 small eggs ill-provided with yolk. From the latter arise the larvae 

 swimming in the albumen of the cocoon, while from the richly- 

 yolked eggs come directly segmented embryos (as in Gnathobdellidse 

 and Rhynchobdellidae respectively). As to the formation of the egg, 

 compare the data of Horst, Beddard, and the reviewer. The 

 spermatozoa develop completely in special organs, which were formerly 

 described as vesiciila: seviinales, instead of which the reviewer, for weighty 

 reasons, has proposed the name sperm-sacs. The same function and 

 origin is possessed by the egg-sacs, which are unpaired only in rare cases 

 (Enchytraeidae), but usually present in one to two pairs. Special sperm- 

 ducts are known in all Oligochaeta, for in the opinion of the reviewer 

 the statement that Aeolosoma discharges the spermatozoa through the 

 nephridia lacks confirmation. The ducts are developed in one 

 or two pairs, and consist of a funnel and a long canal which usually 

 passes into a terminal chamber, the " spermiducal gland." When the 

 sperm-ducts are present in two pairs, they join into a common canal 

 and open outwards through a pair of outlets. One species, called by 

 Beddard Phreorydes smithii, forms an exception ; here the four ducts 

 open outwards independently of each other. The originally-described 

 species of Phreorydes (P. menkeanus and fiUfofniis) are quite unknown 

 in this respect. Special oviducts are not found everywhere ; in 

 Aeolosoma and Naidomorpha simple openings function as oviducts ; 

 these, according to the opinion of the reviewer, correspond to the 

 original funnels, as is the case in Enchytrasidae and Tubificidae. 



With regard to the homology between the nephridia and the 

 sexual ducts, Beddard seems to have superseded E. R. Lankester's 

 old view, according to which each segment contained several pairs of 

 nephridia, one pair of which took upon themselves the functions 

 of the sexual ducts. On the contrary, he turns to the newer 

 developmental researches of the reviewer, according to which the 

 funnels of the ducts proceed from the peritoneum, so that there is 

 no homology between these organs.^ 



As auxiliary organs to sexual intercourse in the various Oligochaete 

 families there are the atria (spermiducal glands, Beddard), the setae, 

 and the penes, which are all described in detail by Beddard, as are 

 also the manifold relationships of form and position of the sperma- 

 tophores, of the spermathecae, of the clitellum, of the sexual papillae, 

 and of the cocoon. 



1 Compare also Goodrich's last paper "On the Coelom, Genital Ducts, and 

 Nephridia." Quart. Joxirn. Micros. Sci., 1895, pp. 477-510. 



