DESCRIPTIONS OF GENERA AND SPECIES 



177 



probably sense-organs ; they lie close to the brain, and in front of the mouth- 

 opening. The setae are, in all the species of the genus except three, capilliform ; 



Fig. 36. 



they are implanted in bundles, of which there are four to 

 each segment ; each bundle contains a varying number of 

 setae, of varying sizes, from two to nine ; the number of 

 setae in the breadth is, in some cases at least, a cha- 

 racter of specific importance. The only species in which 

 there is any specialization of the setae are A. tenebrarum, 

 A. niveum, and A. leidyi; the posterior segments of 

 these species have y-shaped setae, which may or may 

 not be bifid at tips. The body generally, and the pro- 

 stomium especially, has minute, hair-like, rigid processes, 

 which may be of a tactile nature 1 . 



The epidermis is covered by an excessively thin 

 cuticle, only recognizable (according to VEJDOVSKY) after 

 treatment by reagents. The cells of the epidermis are 

 of two kinds ; there are more columnar cells, among 

 which lie large, round, glandular cells. On the ventral 

 surface of the prostomium the ciliated cells are figured 

 by LEIDY (6, PI. ii. fig. n) and VEJDOVSKY (24, PI. i. 

 fig. 36) with a hexagonal contour. The gland-cells are 

 of two kinds, coloured and colourless. The coloured 

 epidermic gland-cells are highly characteristic of the 

 genus ; they are found in every species of this genus, 

 and Ctenodrilus. which is possibly an ally of Aeolosoma. 

 Their colour varies according to the species ; they are 

 red-brown in A. quaternarium, &c., olive green in 

 A. tenebrarum, bright green 2 in A. varium, and bright 

 green with a bluish tinge in A. Jieadleyi. The colour is 

 due to a large drop of oily substance within the cell ; stomium - 3- Muscular ceil*. 4- cm- 



ated pit. 5. Brain. 6. Pharynx. 



that this drop is of a fatty nature appears to be shown 

 by its black staining with osmic acid. The pigment itself 



AEOLOSOMA, HEAD END. 



(After Vejdovsky.) 

 2. Cilia on under surface of pro- 



7. End of pharynx. 8. First pair of 

 nephridia. 9. Oesophagus. 10. Coe- 

 lomie corpuscles, n. Second pair of 



is probably closely related, in spite of its difference nephridia. u. Setae. 13. intestine. 



- . . ,, . T , 14. Coloured oil-globule in skin. 



of hue, in all species; I have shown (32, 74) that 



1 VAILLANT (6) states that there are cilia over the general body-surface. This, however, is contrary to 

 the statements of other authors and to my own observations ; the cilia are limited to the prostomium 

 and to just behind mouth. 



1 The green colour suggests chlorophyll ; ZACHARIAS has recently suggested that the oil g'.obules ' 



A a 



