PREFACE. xni 



I. p. 196. The distinct sexuality (p. 197, 198) of this class has 

 been further extended by CoHN, who has also discovered a second 

 mode of propagation by the so-named winter-eggs. See his paper 

 Ueber die Fortpflanzung der RddertJiiere, in V. SiEBOLD and Koell. 

 Zeitschr. vii. p 431—486. 



The very difficult investigation of the generative system in 

 several of the abranchiate ringed-worms has of late years engaged 

 the attention of M. D'Udekem. In Lumhricus terrestris he has 

 made the discovery of the ovaria and ova hitherto unknown. The 

 ovaries are extremely minute vesicles situated one on each side of 

 the nervous chord in the 12th ring of the body. They are pear- 

 shaped, closely united to the membranes of the chord by their 

 anterior broad extremity and terminate backwards in a canal, the 

 oviduct, which is believed to open with the vas deferens, but was 

 too delicate to be followed to its termination. The ova are quite 

 microscopic. The testes are six in number, three on each side of 

 the intestinal tube, the anterior pair in the 8th ring, the middle 

 pair in the 9th ring, the posterior and largest pair in the 10th and 

 11th rings. Between the testes and the mid-plane are two ciliated 

 infundibula, with the anterior of which the two anterior testes com- 

 municate, with the posterior the posterior testis. The two infundibula 

 on each side are the internal extremity of canals which, after many 

 convolutions, unite to form a vas deferens, which runs backwards to 

 terminate in a transverse orifice on the 15th ring. There are also 

 accessory organs : two hollow spherical bodies on each side attached 

 to the ventral wall by a short pedicle, which is the duct by which 

 they open externally; these were supposed by Duges and others 

 to be the testes on account of their containing spermatozoa, but 

 are called by D'Udekem spermatic reservoirs, having no com- 

 munication with the interior of the lumbricus, and therefore re- 

 ceiving the spermatozoa from without. The remaining accessory 

 bodies, situated like the last on the outer aspect of the testes, are 

 a variable number of vesicles in pairs from the 8th to the 11th 

 ring; they are setigerous glands modified for the secretion of 

 matter to form capsules for the ova [glandes capsulogenes). The 

 earth-worm is oviparous, and the number of ova included in a 

 capsule is 2, 3, 4 or more, though usually one alone is developed. 



In Enchytrceus the testis is single and situated below the intes- 

 tinal tube; it extends from the 11th to the 13th ring. It has the 



