35 



10. Organs of Generation. 



In full grown specimens we often find, as before mentioned, that the arms at some 

 distance from the base exhibit a very remarkably strong enlargement; the dorsal skin rising 

 high" above the subjacent ambulacral skeleton, while it otherwise lies more or less closely 

 on the same (Tab. I, fig. 12, Tab. II, fig. 1). On slitting the skin it will be found that 

 the cavity of the arms (coelom) is here stretched by a very voluminous mass divided into 

 numerous lobes and branches, which in different individuals exhibit a somewhat different appear- 

 -ance. This mass represents the organs of generation, which in some individuals appear as 

 ovaries and in others as spermaries. Both sorts of organs of generation are easily distin- 

 guished from each other., partly by the color and partly by the manner of ramification; but 

 else they occupy the same place in the Cavity of the arms, without ever extending into the 

 coelom of the disc. By spreading on each side the dorsal skin when slit in the middle, 

 and pushing asunder the various lobes or ramifications .from each other (see Tab. Ill, 

 fig. 4, 17) it is easy to ascertain that what appeared at first glance to be a confused mass 

 of lobes, belongs to 2 organs, lying symmetrically on each side of the medial line, each of 

 which is attached only by one point to the interior of the skin. On examining the skin at 

 this place more closely, an evident exterior opening will be discovered (see Tab. I, fig. 12 a, 

 Tab. Ill, fig. 25 c c) surrounded by tuberous projecting borders, which is the issue for the 

 sexual products. These exterior apertures for generation are usually situated quite sym- 

 metrically, one on each side of the arm nearer to the lower side, and distant about one 

 diameter of the disc from the base of the arm. When once their position has been noticed, 

 it will never afterwards be difficult to find them on any arm, without proceeding to any dis- 

 section. 



a. The Ovaries. 



The ovaries have usually (see Tab. Ill, fig. 4) the form of more or less elongated 

 and ramified cylindrical tubes which at last unite themselves on each side to a common 

 short trunk attached to the inside of the skin and containing the short exit passage (oviduct) 

 through which the mature ova are ejected from the body. Sometimes several such ovarian 

 tubes are blended together in the form of large irregular sack-like enlargements, whereby 

 the whole ovary acquires a more crowded and compact appearance (see fig. 5, 6). These 

 enlargements may then either begin with ovarian tubes in the usual form (tig. 7) or they 

 may exhibit only small rounded lobes (fig. 8) or even only form simply rounded reservoirs 

 (see fig. 5). Even in the smallest specimens I have been able to examine, I have found 



5* 



