BOWELL : ANATOMY OF VITBEA SCHABFFI. 55 



mandible is not very prominent ; it appears to originate by chitinisa- 

 tion of the fibrous ends of tbe muscle. The short elasma is connected 

 with the sheath of this same muscle. In Fig. 3, A represents the 

 maxilla seen from the back ; the W -shaped portion shaded darker, 

 which projects considerably, is the attachment of the muscle. 

 B shows the appearance of the organ as viewed from below; the 

 semicircular foundation is seen through the transparent 'beak.' 

 C shows the maxilla in the aspect in which it is usually figured. It 

 is right to point out that few drawings give any idea of the complexity 

 of this remarkable organ. In the present species it consists of four 

 distinct elements, and in the large Helices there are five. It is 

 possible to separate these by carefully treating with sodium hypo- 

 chlorite. It can then be seen that the odontognath mandible conceals 

 a leiognath or oxygnath one. Calcareous granules are usually to be 

 noticed (unfortunately for microtome knives) in the tissues round the 

 chitin-forming parts, and seem to be in some way concerned with the 

 process, which may be of a degenerative character. I shall be very 

 glad to hear from anyone who is making a study of the chemistry of 

 chitin and the histological processes involved in its deposition. 



One millimetre. 



Fig. 3. 



Though the glands which discharge into the buccal cavity are called 

 salivary glands, the nature of their secretion does not appear to be 

 accurately known. The large organ in the centre of Fig. 2 (the 

 ' crop ') is also provided with glands (not shown). Only a part of the 

 pyloric glandular apparatus is shown in the figure. The nephridium 

 is subtriangular ; it has the curious property of staining with borax 

 carmine much more readilj^ than the other tissues. This and the 

 heart are shown here merely to indicate their general position. 



Fig. 4 shows the radula, which is probably sufficient for identifying 

 the species. The noticeable points about it are : («) the small number 

 of marginals; 7 or 8 as against the 10 or 12 usuallj^ found in the 

 species of this group. Juvenile specimens of cellaria might have only 

 7 or 8, but their centrals and laterals are of an easily recognisable 

 type, (h) The shortness of the cusps, in consequence of which the 

 rows hardly overlap at all. (c) The transitional or third lateral is only 

 distinguished from the marginals by a very slight bicuspidation. The 

 central teeth resemble those of V. hihernica, and the general con- 

 figuration of the basal plates is also similar. The radular variation, 



