104 M. L. Plate on Ectoparasitic Rotatoria 



(fig. 1, m^)^ smooth (like all the muscles), which traverse the 

 trunk on each side and can be traced into the third segment 

 of the neck. They originate somewhat behind the middle of 

 the trunk, and are continued backwards in it on each side by 

 two closely approximated muscles (fig. 1, vt') . If we examine 

 Paraseison from the ventral surface we see, outside of the con- 

 tractile bands just described, on each side another one of 

 smaller size, which, however, traverses only the anterior half 

 of the trunk. Within the neck-retractors, marked wi*, there 

 are further two thin muscles, which commence at the base of 

 the neck and penetrate deeply into the tail near the median 

 line. Of the retractors of the caudal segments there are two 

 on each side especially developed, the course of which may be 

 seen in fig. 1, m'^ and m^. How far they extend posteriorly I 

 have omitted examining. Dorsally from these, two bands are 

 extended on each side, of which one {m'') is delicate and short, 

 while the other {m-^) consists essentially of two muscles, which 

 meet together at an angle, and of which the anterior one is 

 distinguished by its shortness and breadth. Besides those 

 mentioned above, the tail contains some other muscles, which 

 serve to introvert the hindmost segments. Thus we have the 

 band indicated by ?n" in figs, 4 and 7 (which possibly forms 

 a continuation of m* or m°), as also m" and m^\ The great 

 muscle traversing the trunk (««*), which is inserted in the 

 middle of the third ring of the neck, is followed anteriorly by 

 ni^ (fig. 2), the anterior point of attachment of which is at the 

 base of the head. This muscle draws back the first two 

 neck-segments, and is assisted therein by the smaller bands 

 (fig. 2, m-^ and ni!^)^ the position and arrangement of which is 

 shown in the figure. All the longitudinal muscles just 

 described are in pairs, and symmetrically arranged to right 

 and left. This applies also to the three short adductors which 

 introvert the most anterior part of the head. Two of these 

 (fig. 6, wi" and w") lie above the masticatory apparatus, the 

 third pair (wi") below it. 



Having described as accurately as possible the organization 

 of Faraseison asplaiichnuSj the description of the other three 

 species of the same genus which occur on the Nehalice of the 

 Bay of Naples may be managed with few words, as, except 

 in a few particulars, they perfectly agree with the above 

 species. 



2. Paraseison nudus^ sp. n. 



This form is distinguished especially, so far as I could see, 

 by the entire absence of the four groups of tactile seta3 which, 

 in the ordinary species, surround the mouth ; conseq^uently, in 



