LEODICID^ OF THE WEST INDIAN REGION. 5 



color is due to pigmentation or to the blood. The body (especially in the forms 

 with little pigment) is tinted red by blood and when there are large gills filled 

 with blood they give the surface a bright-red color which disappears after preserva- 

 tion. If two species have this same structure, their color differences are negligible. 

 Pigmented species, on the other hand, are easily distinguishable, though the 

 pigmentation is not always retained after preservation. 



2. Prostomial structures: It is customary to speak of the prostomium as 

 the "head" of the animal. Even if it were accurate to designate as the "head" 

 a portion which does not surround the mouth, it leads to accuracy of description 

 if we speak of the "head" as the anterior end of the body, making a distinction 

 between the prostomium and the peristomium. The prostomium is a rounded 

 lobe overhanging the mouth, and to which appendages may be attached. In 

 the Leodicidce these appendages are the palps and the tentacles. The former 

 when typically developed are fleshy appendages attached to the lower anterior 

 surface of the prostomium. The latter are more or less elongated slender append- 

 ages attached to the posterior dorsal surface of the prostomium. In a few genera 

 (see Omtphis, plate 7, figure 2) a pair of rounded processes arise from the anterior 

 margin of the prostomium and are generally known as the "frontal tentacles." 

 Pruvot (1885, p. 261), in connection with work on the central nervous system of 

 the Leodicidce, studied the innervation of these organs in Hijalinoecia and decided 

 that their nerve supply indicates that they are homologous with the palps rather 

 than with the tentacles. The palps are most in evidence in Stauronereis (plate 9, 

 figure 21), where they are long, rather heavy, and more or less wrinkled. It seems 

 evident that a bilobed condition of the anterior margin of the prostomium, when- 

 ever it occurs in other Leodicidce, arises from a fusion of the palps with the anterior 

 margin of the prostomium, the degree of the lobing varying inversely with the 

 amount of the fusion. In the Lumhrinerei^xce there is never any trace of a lobing. 



In some species of Leodice the prostomium has a four-lobed character, the 

 halves being each subdivided into an inner and an outer lobe, the former the smaller. 

 Pruvot and Rachovitza (1895, p. 416) assert that the innervation of these two 

 lobes indicates that the larger is the palp and the inner is homologous with the 

 frontal tentacle of such genera as Onuphis. On the posterior margin of the pro- 

 stomium there may be seven, five, three, one, or no tentacles. Since we may have 

 at one end of the scale no prostomial appendages and at the other as many as nine 

 (including the palps), the question arises as to which was the primitive condition. 

 Does the four-lobed character in some Leodice, for example, represent the first 

 stages in the development of palps and frontal tentacles such as appear in Onuphis, 

 or has there been a fusion of appendages, and do the Lumhrinereince represent the 

 latest stage in this process? In the general character of its body and the structure 

 of its jaw Stauronereis seems to be more primitive than the others, so that I believe 

 (lacking embryological evidence bearing on this question) that, in so far as the palps 

 are concerned, there has been a fusion. If we regard Stauronereis as a primitive 

 form, we must assume that in the matter of tentacles the evolution of the family 

 was in two directions. Eyes are usually present near the posterior border of the 



