ANATOMY AND LIFE HISTORY OF MOLLUSCA. 125 



In a great number of Gastropoda which I have examined, 

 including the following species, I have found red fluids in the 

 buccal masses surrounding the jaws : — Patella tramoserica, 

 and the other littoral species already mentioned, such as Acmcea, 

 Siphonaria, Risella, Trochocochlea, Senectus, many species of 

 Trochus : in fact, I do not remember having met with any species 

 in which the buccal mass had not a blood-red color. The 

 appearance around the jaws is just that of raw flesh, but a minute 

 examination shows that the red portions are not universally 

 distributed, but confined usually to the terminations of the bands 

 of muscles. If the buccal mass of any of the Gastropods is placed 

 under the microscope, it is seen to consist of a number of long 

 narrow bands, red at the ends. The spindle-shaped cells are 

 often greatly elongated and band-like in form, surrounded by a 

 membrane. There is no differentiation of those singly and doubly 

 refracting particles, giving the appearance of transverse striation. 

 In all the species I have examined the band-like fibres prevail.* 



Before leaving the subject of the buccal mass, it will be well to 

 deal with the cartilages which support the Radula, which in the 

 most of the Gastropods is the only representative of the internal 

 skeleton. In the Trochidse, Patellidse, Littorinidae, and many 

 other families, there are two oblong pieces of cartilage, raised at 

 the edges with a central broad groove in which the Radula lies. 

 The shape of these two pieces of cartilage is somewhat pointed at 

 the extremity, like a tongue in fact. In Senectus gruneri there 

 are four pieces of cartilage ; that is to say there are two small 

 pieces added on to the posterior end of each jaw, and working 

 with a hinge-like movement. In other species, the extra cartilage 

 is reduced to a mere tubercle, but there is much variety. 



In the Siphonostomata, where the buccal mass is contained at 

 the mouth of a more or less long contractile siphon, the arrangement 

 is very different. Taking Triton spengleri, Lam., a common species 

 at Port Jackson, as a type, we find a simple tube of thin cartilage 

 surrounded by two muscular coats, one lining the inside and the 

 other the outside of the much thicker cartilaginous siphon. The 

 cartilaginous jaws in the buccal mass are hood-shaped and meet 

 together over the Radula, a part of which is exposed in a kind of 

 little orifice, and where it works backwards and forwards on the 

 particles of food which are exposed to its action. The hooded 

 cartilaginous jaws are bound round with a series of band-like 

 muscles ; one transverse band passes over and under them about 

 half-way from the orifice or fissure where the hood-like jaws meet. 



*Mr. G. Tryon, in his " Introduction to the Study of Mollusca/' (Vol. i., 

 p. 90,) says that in Area pexata the blood is red, and is commonly called 

 " the bloody clam." He speaks also of the coloured blood of all the species 

 of Planorbis. 



