BRITISH NEMERTEANS, AND SOME NEW BRITISH ANNELIDS. 341 



that it is very short, and bears an " isolated" stylet, while his enlarged drawing* 

 is incomplete. 



M. de Quatrefages considered the posterior chamber of the Ommatoplean 

 proboscis the intestine-proper, but there is no support for this view ; and, indeed, 

 his minute anatomy of the organ is somewhat inaccurate. I have not observed 

 that the dilatations and contractions of the channels of the reservoir (his oeso- 

 phagus) vary in the manner he refers to in different species. He describes two 

 bulgings of this " oesophagus," a large lozenge-shaped one at its commencement, 

 and another corresponding to our reservoir, these dilatations being connected by 

 a straight channel. The former may refer to 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 see any longitudinal fibres. I have always 

 been able to see these fibres in the fresh and living animals without any addition 

 to the sea- water in which they happened to float ; and, moreover, the presence 

 of longitudinal, looped, and other fibres previously described show how much 

 more complex the structure is than this author imagined. He correctly reports 

 the absence of vibratile cilia from this region ; but he again errs by affirming that 

 they occur in the posterior chamber. His figures of the stylets are different from 

 any seen by me, since they exhibit a bulging and then a contraction in front of 

 the head. The basal sac is termed the " body" of the central stylet, and he narrates 

 how in Nemertes balmea (our 0. gracilis) this body has an exterior coat com- 

 posed of the same structure as the point. Nothing more than the usual firm 

 muscular setting is really present (see p. 335). Again, the statement that the 

 "body" acquires greater solidity is not borne out in fact, for the granular con- 

 tents of the sac are homogeneous 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 Polia, he considers its existence likely. The author has 

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

 fixed in a clear setting 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 Polia; 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 



* Memoires l'Acad. Roy. &c. pi. iii. fig 6. 

 VOL. XXV. PART II. 4 S 



