GENERATIVE SYSTEM OF THE EARTHWOEM. 237 



organ is not ciliated internally, but its walls are capable of contracting 

 vermicularly or peristaltically. 



(616.) The vascular system in connexion with this apparatus is at 

 certain seasons extraordinarily developed. When present under the 

 most evident circumstances, it may be described as consisting of three 

 parts. First, of two or three large vessels, which curve upwards from 

 the ventral to the dorsal trunks. These vessels thus form a framework 

 by which the slender ciliated tube is held vertically in situ, they them- 

 selves being vertically disposed. 



(617.) Between the primary vertical trunks extend a vast multitude 

 of secondary branches, which further subdivide to form a dense plexus 

 of smaller vessels, in the meshes of which the ciliated tube is entangled. 

 At certain seasons and conditions of growth, a dense mass of florid blood 

 is attracted to and retained in the region of the segmental organs. It 

 is contained at these times, not in ordinary cylindrical vessels, but in 

 capacious lateral csecal branches, terminating in large, bulbous, pear- 

 shaped extremities, evidently constituting a special provision, the nature 

 of which still remains a matter of conjecture. 



(618.) The sexual system of the Earthworm we have already found to 

 be centred in a particular region of the body, indicated by the thickened 

 glandular collar above alluded to, which, however, on close examination, 

 is found to be situated several segments posterior to the generative 

 masses contained within. 



(619.) Now, in studying the visceral contents of each ring within 

 the limits of the generative region, it will be best to proceed from be- 

 hind forwards. The dissector thus comes first upon the largest and 

 most prominent of all the generative masses. They are testes, as may 

 be proved by a microscopic examination of their contents. They have 

 a white, glittering, oily colour. In figure they are intestiniform, the 

 coils, of which there are two or three, being tied together by a kind of 

 mesentery and enclosed in a membranous capsule. These two testi- 

 cular masses, which lie across and fill up several rings, may be traced 

 with perfect clearness to comparatively narrow peduncles, which, when 

 minutely and successfully dissected, will be found to connect themselves 

 intimately with the roots of the ciliated tubes or special segmental 

 organs of the same annular spaces ; or, in other words, the tube and the 

 peduncle of the testicular mass have a common outlet. This outlet 

 cannot be detected on the external surface of the worm ; it is far too 

 minute and closely contracted ; but its position may be clearly ascertained 

 by the termination, internally, of the ciliated tube, proving, according to 

 the views of Dr. Williams, that the generative gland is an outgrowth 

 from, and organically the development of the ' segmental organ.' The 

 two ciliated tubes, one on either side, which are contained in this tes- 

 ticular ring, differ in no respect from those of the non-generative rings 

 but in that of size. They are considerably larger than the latter. 



