288 BULLION. 



The greatest variations are in the number of the nervous 

 ganglions, the salivary glands, gizzard, and the " organe exci- 

 tateur ;" these we will briefly mention. The central flat white 

 retractor of the head and the lateral cesophageal threads are 

 nearly similar. In this species the two principal masses of 

 the ganglionic cordon consist of three distinct pink lobes on 

 each side, instead of two as in its I had almost said congener, 

 B. hydatis ; the two minute buccal and stomachal ganglions 

 are nearly similar in shape, position, and in their connection 

 by nervous cords with their primary points of departure. 

 The very strong gizzard, which is the stomach, is formed of 

 three white, testaceous, subtriangular plates, two of which are 

 of the same size and shape, the third or key-plate is smaller, 

 all being pointed at both ends, enclosing a strong brown 

 circular membrane, which receives the O3sophagus, from which 

 the duodenum departs. The salivary glands, instead of, as in 

 B. hydatis, being very long and springing from the gizzard, 

 are two short corrugated fillets, which originate on each side 

 anterior to the nervous collar, their extremities floating free. 

 If M. Cuvier had not determined these appendages to be the 

 organs of deglutition, we should have demurred to such views, 

 and rather have considered the lateral leaflets around the 

 mouth to be the salivary glands, which, being present in the 

 three species of the Bullida I have examined, prove that 

 they are not accidental markings, but secreting glands; of 

 what nature is doubtful. The " organe generateur " or " ex- 

 citateur" greatly differs in form in the two genera, which, 

 however, can only be considered as a specialty, since its 

 function, position, mode of protrusion and retraction, and 

 isolation from the testis, are absolutely the same; but in- 

 stead of being trifid and comparatively short, as in B. hydatis , 

 it is, in a moderate-sized animal of B. aperta, at least 3 

 inches long, slender, or rather filiform, cylindrical, rolled in 

 short folds into an irregular mass, affixed and in connection 

 with the orifice under the right segment of the head, and 

 lying, when inactive, under the anterior part of the cavity 

 of the gizzard; it can be protruded and withdrawn as the 

 finger of a glove can be inverted and again exserted. It 



