PROBOSCIS. 71 



some connection with the mobile muscular chamber behind the stylet-aperture in the floor of the 

 anterior region, but his descriptions and drawings are indistinct. He aptly likens the two central 

 divisions (stylet-region) to crystal ; but he says he required the action of hydrochloric and acetic 

 acids to distinguish fibres, which, he observes, have a transverse direction, and he especially notes 

 that he could not make out any longitudinal fibres. I have always been able to see these fibres in 

 the fresh and living specimens, without any addition to the sea-water in which they happened to 

 float ; and, moreover, the presence of longitudinal, spiral, and other fibres, previously described, 

 show how much more complex the structure is than the author imagined. He correctly reports 

 the absence of vibratile cilia from this region ; but he errs by affirming that they occur in the 

 posterior chamber. His figures of the stylets differ from any seen by me, since they exhibit a 

 swelling and then a contraction in front of the head. The basal apparatus is termed the "body" 

 of the central stylet, and he narrates how in Nemertes balmea [N. gracilis, Johnst.) this body has 

 an exterior coat composed of the same structure as the point. Nothing more than the usual firm 

 muscular investment is really present (see p. 67). Again, the statement that the " body" acquires 

 greater solidity is not borne out in fact, for the granular contents of the apparatus are homo- 

 geneous throughout. He speaks of a pouch containing a granular glandular substance in which 

 the stylet and its " body" are placed in this species, and thinks it probably secretes the latter 

 (body) ; and, though he has not seen it in Folia, he considers its existence likely. The author 

 has evidently fallen into confusion here, for the granular structure (or so-called " body") is fixed 

 in a clear investment of the firm muscular substance. He next describes and figures other two 

 cavities, which are said to exist at the borders of the "stylet-pouch," semi-opaque and glandular 

 in N. balmea, very transparent in Folia; and he considers that these two glandular organs secrete 

 a poisonous fluid, for use in offence and defence, which (fluid) is poured into the pit in front of 

 the stylet-region. Entomostraca, moreover, were killed instantaneously by wounds of the stylet, 

 an effect which could not be due to mechanical injury only, but to the presence of an active poison. 

 It is true he was not able to distinguish these glands or their cavities in many species, so that, if 

 they existed, they must have been confounded with the neighbouring tissues by reason of their 

 transparency. Such glands have never occurred in the British species, and the opaque granular 

 substance really present in N. gracilis (JV. balmea, Quatref.) totally differs in structure and 

 function from his representations. The folding downwards of the floor of the anterior chamber, 

 and the presence of the muscular space behind, have probably caused the mistake; and, indeed, 

 it may be remarked, that the time and opportunities necessary for a correct appreciation of these 

 complex structures make those best acquainted with them least surprised at such errors. The 

 two muscular bands, also, which M. de Quatrefages figures and describes as for the probable 

 purpose of carrying forward the stylet-apparatus, and compressing his hypothetical poison-glands, 

 have not been seen, and the explanation of the parts already given renders such useless. With 

 regard to the observations that the marginal stylet-sacs are free in N. balmea, but placed in the 

 thick walls of the " oesophagus" in Folia, I can only state that the type of structure is the same 

 in all, and that they occupy corresponding positions in the species referred to. It is probable 

 also that the finding of only one marginal stylet-sac in Folia quadrioculata and P. Jiwnilis was 

 accidental, and- not by any means characteristic of such species {Tetrastemmce) . The remark, 

 that in Folia vermieulus one sac is placed on the dorsal and the other on the ventral surface, is of 

 no consequence when the ever-changing condition of this very mobile organ is remembered. The 

 author further describes the " intestin" (our posterior chamber) as having the same coats 



