of the Bay of Naples. 91 



unless we are to interpret as such a pyriform thickening of the 

 hypodermis situated in the tail in the median dorsal line. 

 The cuticle is not of homogeneous constitution throughout, 

 but presents some remarkable conditions of structure. ^ In the 

 segments of the neck we find a very delicate longitudinal 

 striation (fig. 2) formed by many parallel lines, and which, 

 spreading out like a brush, also extends upon the posterior 

 part of the head. Instead of this there is, upon the posterior 

 parts of the trunk, an apparent granulation, which also covers 

 the whole of the foot. As we see by considering an ideal 

 transverse section at the margin of the body (fig. 3), this is 

 produced by small rounded or elongated hollow spaces which 

 are placed close together, and frequently, arranged in longi- 

 tudinal rows, traverse the inner part of the cuticle. It the 

 punctuation of the tail be carefully examined, it is seen tliat 

 on the two hindmost apparent segments it suddenly becomes 

 much weaker than on the preceding ones. _ Further, the skin 

 of the penultimate caudal ring is distinguished by the pos- 

 session of a striation which is very noticeable. Four sharply 

 marked lines run parallel to each other and not far apart troin 

 the dorsal towards the ventral surface and obliquely from 

 before backward (tigs. 1 and 7). Those of the right and left 

 sides do not meet in the median dorsal line, but leave between 

 them a narrow band of the ordinary texture. The ventral 

 surface of the same segment bears the aperture of a peculiar 

 organ, which also occurs in Seison, but for which I cannot 

 with certainty indicate a homologue in the other Rotatoria. 

 Glaus says of it {I. c. p. 82) :— " A pretty strong efferent 

 duct opens in front of the adherent disk, on the convexly 

 curved ventral surface of the terminal piece, upon a small 

 conical tubercle." It is a small roundish vesicle, composed 

 (it seems to me) of a structureless membrane, and it opens by 

 a short duct projecting a little beyond the rest of the skin 

 (figs. 4 and 7, /). Frequently it was tensely filled with a 

 limpid fluid, whilst at otlier times the walls lay loosely in 

 contact. With all my efforts 1 have never been able to 

 observe any contractions of it, and therefore believe that none 

 take place. In the freshwater genera 3Ionocerca and Diurelta^ 

 the adhesive glands of the foot are converted into vesicles 

 with contractile walls, which can suddenly evacuate their 

 secretion. Possibly we have here to do with a corresponding 

 arrangement which has become rudimentary, and then this 

 organ would have to be regarded as a modified pedal gland, 



* L. riale, "Beitriige zur Natui-gescliichte der Rotatorien/'iu Jenaische 

 Zeitschr. f. Naturw. Bd. xix. N. F. xii. pp. 50, 51. 



