ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 245 



Organization of Echiurus Pallasii.* — Dr. Spengel continues his 

 valuable essays on the characters of the Gephyrea by an account of his 

 observations on this form. 



Commencing with an account of the clermo-muscular tube, the 

 author points out that the dermis consists of an epidermis, a covering 

 cuticle, and an internal cutis. These parts are different on the trunk and 

 on the cephalic lobes. Unicellular glands, pyriform in shape and with 

 a more or less long neck, are arranged with a good deal of regularity 

 on the trunk ; they are arranged in groups, which form papilliform 

 elevations. These papilla are set in transverse series around the 

 body, and rings of larger papillae may be found to alternate with three 

 or five rings of smaller ones. The structure of these parts seems to 

 be very difficult to make out, but in the centre of each a pore may be 

 distinctly seen, and round about it there are a number of bright spots. 

 The pore leads into a short canal, which is bounded by a number of 

 cells, some of which are undoubtedly glandular in character ; others 

 would seem to have a sensory function ; well-developed nerve-branches 

 pass into the papillae. The cutis of the trunk forms a connected layer 

 of varying thickness, consisting of a gelatinous homogeneous ground- 

 substance, in which stellate cells, connected one with another, may be 

 made out, together with " balls " of cells, which are filled with reddish- 

 brown or yellowish pigment-granules. In the cephalic lobes there is 

 a difference between the characters of the dorsal and of the ventral 

 portions of the dermis, for the latter has a ciliated cylindrical epithe- 

 lium, placed in lines along its lateral and anterior margin. 



The muscular tube consists of three layers ; the outermost is 

 formed of circularly set fibres, then follows a layer, three or four . 

 times as thick, of longitudinal fibres, and the third, which is again 

 thinner, has an oblique direction ; and the whole system is bilaterally 

 symmetrical on either side of the middle line of the body. This ex- 

 cessive development of the contractile layer explains the wondrous 

 variations in form of which its possessor is capable. Towards the 

 posterior end the circular muscles are alone well developed, and there 

 they appear to take on the function of a sphincter. On the other 

 hand, although there are some changes in the disposition of the parts, 

 the musculature is excessively well developed in the region of the 

 cephalic lobes ; and in addition a number of delicate dorso-ventral 

 muscles are developed. 



Two kinds of setae are found in EcMurus. The first set consists 

 only of two (the " unguiculi genitales " of Pallas) ; in either of them 

 there is a cylindrical shaft, about 6 • 5 mm. long in the adult, and a 

 curved hook of 2 • 5 mm. The latter is of a golden yellow, and the 

 former of a whitish colour. The hook would appear to be structure- 

 less, but the shaft gives indications of being made up of a number of 

 fine fibres. Each seta is surrounded by two sheaths ; the inner one 

 is chiefly formed by an epithelium directly continuous with the epi- 

 dermis ; it is, in fine, the setal follicle. The component cells shed 

 out a cuticle; the outer sheath is similarly bilaminate, its homo- 



* Zeitsclir. wiss. Zool., xxxiv. (ISSO) pp. -160-538 (4 pis. aud 2 figs.). 



