300 BULLETIN OF THE 



and meets and is joined to a corresponding spur from the outer 

 tunic of its neighbor. These diverticula are hollow, and the blood 

 passes into and out of them ; but the cavity of each is separated by a 

 partition from that of the one to which it is joined, so that there is 

 no communication between the sinus systems of adjacent zooids. 

 Each is furnished with eight of these spurs, by two of which it is 

 attached to the neighbor in front of it on the same side of the chain ; 

 two serve to join it to the one directly behind it ; two unite it to the 

 neighbor obliquely in front on the opposite side of the chain ; and the 

 remaining two connect it with the one obliquely behind it. When 

 the chain is quite young, the test is thin and the surface curved at 

 all points, and the spurs project some distance beyond it, and thus 

 keep the animals apart, and at the same time bind them together; 

 but as they grow larger the tests thicken, embrace, and gradually 

 cover up the spurs, and at last the tests of the two adjacent zooids 

 meet and become flattened by mutual pressure, and tend to force 

 the animals apart, and the chain now falls apart at the slightest dis- 

 turbance; so that a full-grown chain can be found only in water 

 which has been unusually still for some days. Although the motion 

 of the separated zooids is not as active as that of a united chain, in 

 which all the components act together to effect locomotion, they live 

 and flourish when separated, and all traces of the spurs disappear, and 

 the body again becomes rounded and presents the form shown in Fig. 

 3, the outline of which differs in several prominent features from that 

 of the solitary form. The long terminal processes are wanting, and 

 the posterior end of the body is prolonged into a broad, bluntly 

 pointed cone, which contains the digestive and reproductive organs, 

 and is the so-called "nucleus." 



We may state here that the solitary form, which is the female, is 

 hatched from an egg which is carried within the bod}' of the Chain- 

 salpa ; and the Chain-salpse are the males, and are produced by a 

 process of budding from the body of the female, and a single egg 

 passes into the body of each male before birth. 



The outer tunic (Figs. ], 2, and 3, b) conforms to the inner surface 

 of the test, and the two are usually in contact, although they are 

 united only around the edges of the apertures, and may easily be sep- 

 arated from each other. Upon the inner surface of the outer tunic, 

 the ganglion (v) and the muscular girdles (/) are attached. 



