PROBOSCIDIAN CHAMBER. 49 



is correctly alluded to. The reflection of the wall of the proboscis before-mentioned, in front of 

 the ganglionic commissures, is the only barrier (and a very effectual one) that separates the probos- 

 cidian chamber from the tissues of the head. In no species has such a cephalic diaphragm as 

 represented by M. de Quatrefages been found; but the ciliated oesophagus, to be described 

 hereafter, takes its place, and leads one to infer that the distinguished naturalist has misinterpreted 

 the structure. Besides, the head is not a hollow organ, requiring such definition from the other 

 parts of the body. The same author, while explaining a transverse section of Nemertes Borlasii, 

 shows a canal surrounding the proboscis ; but in his description he confounds it with the general 

 cavity of the body, and figures the proboscis occupying the centre of the latter posteriorly. 

 This account, no doubt, refers to one of the Anopla, but he states that the same arrangement 

 occurs in the Amphiporidse, and represents in a JPolia a series of transverse fibres as forming 

 a platform (plancher) at the anterior and upper portion of the general cavity of the body, 

 indicating its presence in his figures by a dark shading. No such arrangement of transverse 

 fibres has been seen by me, but the characteristic ciliated oesophageal chamber occupies this 

 situation. The somewhat erroneous views he entertained with respect to the relations of the 

 corpuscular fluid of the proboscidian chamber may be understood by a glance at one of his 

 figures, which depicts in Folia sanguirubra the proboscidian bodies floating in what he terms the 

 genital cavity, and in which the genital caeca are supposed to lie. I cannot corroborate his state- 

 ment that these corpuscles become much more numerous at the epoch of reproductive activity. 

 The diminished size of the chamber may cause them to crowd anteriorly, but this is not an 

 increase. Dr. Johnston likewise confounded the proper sheath for the proboscis with the general 

 cavity of the body ; and Dr. Williams, who styled the canal the oesophageal intestine, stated that 

 it opened externally on the side of the body not far from the head, after the manner of the 

 Sipunculidse. M. van Beneden alludes to the sheath in Folia obscura, and compares the fluid and 

 corpuscles to pale blood. Prof. Keferstein does not describe the chamber with sufficient clearness, 

 and mentions that the proboscidian corpuscles are placed in the general cavity of the body. 



The structure of the special corpuscles, and the highly organized condition of the trans- 

 parent liquid in which they float, point them out as being, in all probability, concerned in 

 nutrition, as first mentioned by M. de Quatrefages, though he likewise associated generation there- 

 with. Some very interesting questions, however, are raised by their entire absence in Nemertes 

 carcinop/iila, especially to those who, like the late Dr. Williams, think the fluid analogous to 

 the peritoneal or perivisceral fluid in the true Annelids, a fluid, we may remark, which Professor 

 Huxley considers the true blood, while he imagines the red fluid in the branching vessels 

 analogous to the water-vascular system in the Annuloida. If in Nemertes carcinophila the 

 proboscidian fluid had been more important in nutrition than that in the vessels, it certainly 

 would not have given way to the latter. It is to be remembered, too, that this absence coincides 

 with the atrophied condition of the proboscis itself and all its apparatus. It cannot be affirmed, 

 also, of the Nemerteans, that the fluid in the so-called blood-vessels is devoid of corpuscles, for 

 they occur in several species. Again, I think there can be no doubt the fluid and corpuscles 

 exercise a very important influence on the reproduction of the proboscis, a process hereafter to 

 be described, as well as promote the absorption of the debris of the discarded organ when it 

 happens to be included in the chamber. But, while thus affirming that the fluid has a certain 

 influence on, and bears a certain relation to, the development of the proboscis, it cannot be said 

 to be indispensable to the presence of the latter, since there is a small proboscis in Nemertes 



7 



