4© 



EISEN 



DETAILED DESCRIPTION. 



Body-wall. — The body-wall thin and entirely transparent, without 

 any pigment in any of the layers. The goblet cells in the clitellum 

 large and square and very prominent, giving the clitellum, when viewed 

 exteriorly, a strongly mottled or marbled appearance. 



Testes. — Consist of a number of narrow lobes, as in M. jnirabilis. 

 Sperm -sacs extend as far back as XIV and ovisacs as far as XVII. 



Sperniathecce (p1. xi, fig. i). — Some variation in the size of the 

 various parts. The duct with its small globular diverticles was in one 

 specimen equal in length to the ampulla. In the other specimen the 

 ampulla is much longer and more strongly nipped by the septa. In 

 one specimen the ampulla extended as far back as VIII, but in the 

 other they reached IX. 



Spermiducal apparatus (p1. xi, fig. 3). — The penial bulb hardly 

 encloses any more of the sperm-duct than the pore, at any rate it does 

 not ascend along the duct as in most species. Immediately adjoining 

 the bulb, or in the upper part of the bulb, the atrium is joined by a 

 set of five or more atrial glands. Penial bulb with no glands of any 

 kind ; large glands outside of the bulb extend in all directions around 

 the bulb a distance equalling the diameter of the bulb. Atrium itself 

 only a little wider than the sperm-duct. The length of the sperm-duct 

 could not be ascertained, as there was no specimen to dissect, but judg- 

 ing from sections in which it is seen that the ducts do not extend farther 

 back than XIII, it can be concluded that the ducts are not over twice 

 as long as the funnels. 



MESENCHYTR^US KINCAIDI sp. nov. 

 p1. I, figs. 16 and 17; p1. vii, fig. 7; text-fig. 17. 

 Definition. — Length 21 mm., width .85 mm. Somites 67. Sets 

 sigmoid: ventrals, 4, 5, 6, 7, 8, 6, 7, (XIII) 3, 6; laterals, 3, 4, 5, 

 4, 3, 4 (XII), 13, 4, (2, 2). Prostomium small, somewhat pointed, 

 somite I short. Clitellum XI, XII, XIII, promiiient. Copulatory 

 papilla exteriorly not prominent. Septal glands in IV to VI deeply 

 lobed and consisting of several folds. Brain anteriorly very deeply 

 emarginated, posteriorly convex, broader than long. Dorsal vessel 

 rises posterior to somite XV. Intestine covered with a layer of short 

 thin chloragogen cells. Spermathecse stout, with two diverticles 

 almost as long as the whole spermatheca. Sperm-ducts extend as far 

 back as XVII, thin, but at least seven times as long as the funnels. 

 No atrial glands, no accessory and no penial glands of any kind. The 



