OF THE HOTATORIA. 411 



to the stomach. If, on the other hand, the " oesophageal bulb " be regarded 

 as an accessory stomach containing a dental apparatus, as in the lobster, then 

 the term oesophagus belongs to the tube extending between the mouth and 

 the bulb. The following physiological distinction is, however, noted by Prof. 

 "WiUiamson, who says — " The stomach of the lobster, with its dental append- 

 ages, is that in which the digestive process is carried on. Such is never the 

 case with the pharyngeal bulb of the Eotifera. The digestive sac is situate 

 lower down. The pharjmgeal bulb bears closer affinity to a gizzard, resem- 

 bling that of Bowerhankia and other Bryozoa, differing, however, from that 

 of a bird, which is located helow the " proventriculus " or true stomach. 

 However, some confusion will be removed by avoiding the term " oesophagus, ^^ 

 and, without troubling oiu'selves with the precise homologies of the parts, by 

 naming the tube between the mouth and jaws the '^'pharynx " or " vestibule,^' 

 the jaws themselves with their suiToimding mass the '' maxillary bulb " or 

 mastcuv (Gosse), and the canal between the last and the stomach the pro- 

 ventricular or gastric canal. The name " buccal fiinnel " has been imposed 

 on the tube leading from the mouth to the maxillary apparatus by Mr. Gosse, 

 and might advantageously have been adopted. 



To proceed. The pharynx (XXXYII. 19 a; XL. 23 in) varies much in its 

 dimensions : sometimes it is a narrow tapering tube, and, when contracted, 

 visible only as a double line ; at other times it is wide and short, and then 

 especially deserves the name of ^' vestibule," since it ceases to be a canal. 

 Several peculiarities in itc structure occur in different genera, — the most re- 

 markable in Floscularia c.nd Stephanoceros. In the former genus, the oral 

 cavity (infundibilum, Dobie) is separated fi'om the pharynx by a rim armed 

 by non-vibra.tile cilia : the pharynx itself is again subdivided by a fissured 

 partition or diaphragm, in^o an upper space (vestibule), and a lower large and 

 very dilatable cavity, called the " proventriculus " or " crop." The crop ends 

 below in, or in some measi^.re embraces, the maxillary bulb (see woodcuts, 

 Part II.). A similar structure obtains in Stephanoceros. 



In Melicerta Prof. Williamson observed, within the pharynx near its 

 junction with the maxillary .bulb, the ciliated hning membrane " to hang in 

 several loose, vibratile, longitudinal folds ; " and Prof. Huxley, in his account 

 of Lacinularia, gives the subjoined summary of these folds and vah^ilar par- 

 titions : — " A narrow pharjTix leads horizontally backwards from the lower 

 part of the buccal cavity, and becomes suddenly widened to enclose the pha- 

 ryngeal bulb in which the teeth are set (XXXVII. 19a). "VMiere the buccal 

 cavity meets the pharynx, a sharp line of demarcation exists. In Melicerta 

 two cui'ved lines are seen in a corresponding position, and evidently indicate two 

 folds projecting upwards into the oesophagus (pharynx). In BracJiionus these 

 folds are stronger (XL. 1 b), while in Stephanoceros and Floscularia (XXXVII. 

 1 & 19) this partition between the pharynx and what may be called the 

 crop is still more marked. From the inner margin of the aperture in the 

 partition, two dehcate membranes hang doTv^n into the cavity of the crop, 

 which have a wavy motion ; and it is to them, I think, that what Mr. Gosse 

 describes as an appearance of ^ water constantly percolating into the ahment- 

 ary canal ' is due. Dujardin had already noticed these ' vibrating membranes ' 

 in Flosculanay 



Observers coincide in describing the cilia of the oral cavity to extend into 

 and line the pharynx (XL. 23 m). The waUs of this tube are so very dilata- 

 ble, that bodies of very considerable size can traverse it to the maxillary 

 apparatus. In the genera Lacinularia, Melicerta, Brachionus, Noteus, and 

 Tubicolaria, close to the wall, or actually within its substance, as Ley dig 

 represents in Noteus, are two conspicuous structures, described by that author 



