1 22 Mr Thomas A. Huxley on a Hermaphrodite and 



certain observation of the manner in which these vessels termi- 

 nate there. I am inclined to think, however, that they open 

 into a circular vessel, from which the branchial vessels arise. 



It was no less difficult, in an adult specimen, to determine 

 whether a ventral vessel existed or not ; but in a young form, 

 I saw such a vessel communicating with the inferior trans- 

 verse branches, and distinctly contracting. It was superficial 

 to the ciliated canal immediately to be described. 



Of a dorsal vessel I could find no trace. The final ramus- 

 cules of the superior transverse branches of the lateral trunks 

 were found, whenever they could be distinctly observed, to ter- 

 minate caically. There could be no question whatever, that 

 these caecal ends were the natural terminations of the ramus- 

 cules, as the animal under observation had been subjected to 

 no violence, and was viewed by transmitted light. I am the 

 more particular in insisting upon this point, as one might 

 very readily be led, in dissecting annelids, to suppose that 

 caecal terminations of the vessels are much more frequent than 

 they really are. Their vessels, in fact, possess, in a very 

 high degree, that tendency to contract when torn, which is so 

 well known in the arteries of the higher animals. And if under 

 the simple microscope the vessels of an Eunice or Nereid be 

 deliberately pulled asunder, it is most curious to observe how 

 very little of the contained fluid pours out, and how smooth 

 and round the torn ends immediately become. In our Protula, 

 however, the mode of examination was such as to preclude all 

 chance of error from this source ; and I have besides fully con- 

 firmed the fact of this mode of termination,* in the singular and 

 beautiful genus Chloramia, which has the advantage of great 

 transparency. In this animal it is easy to observe that, though 

 many of the ultimate branches of the vessels anastomose, and 

 thus give rise to a network, yet that there are also many branches 

 of no inconsiderable dimensions, which terminate in caecal ex- 

 tremities. Such vessels may be frequently observed coming 

 off from the transverse trunk and hanging freely into the peri- 



* This caecal termination of the vessels appears to reach its greatest develop- 

 ment in the Scoleid genera, Euaxes and Lumbriculus, in which a vessel arises 

 in each segment from the dorsal trunk, and shortly divides into many caecal 

 ramuscules. See Siobold. Vegleichende Anatomie, p. 212. 



