of the Bay of Najples. 89 



Before proceeding to the detailed description of the diife- 

 rent organs, we may, for the purpose of orientation, in the first 

 place glance at the general organization of Paraseison. 



The head agrees very little with the image which the 

 typical Rotatoria present of this part of the body, as it displays 

 no trace of a wheel-apparatus composed of motile cilia. 

 Looked at from the side it has a lenticular form ; broadest in 

 the middle, it tapers off before and behind, bears the small 

 buccal aperture (fig. 1, o) at its anterior pole, and contains in 

 its interior a complicated masticatory apparatus [ma)^ a slender 

 oesophagus {(e) opening dorsally into this, and a large gan- 

 glion [g), which may be regarded as the brain. The neck 

 consists of three segments separated by annular grooves in 

 the cuticle, of which the anterior can each be invaginated 

 within that behind it, and which is traversed throughout its 

 whole length by the oesophagus. Its width gradually in- 

 creases from before backwards. The middle-hodij [trunh) is 

 by far the broadest section of the whole body. In it we find 

 the stomach {st) , which is closed cajcally, and consequently 

 possesses no intestine and anus ; dorsally or laterally to this 

 are placed the paired sexual organs, the unpaired aperture of 

 which is very differently placed in the two sexes. It is 

 always situated on the dorsal surface, in the male at the point 

 where the neck and trunk meet, in the female at that where 

 the trunk passes into the tail (a). The ahdomen^ which 

 follows, gradually becomes narrower posteriorly ; it is com- 

 posed of several apparent segments which can be pushed 

 forward telescopically into one another, and which enclose a 

 number of pyriform mucous glands (_/), whose long efferent 

 ducts open at the hinder pole of the body, and the secretion 

 from which attaches the animal to its surface of support. 



From a passing examination of the object it may seem 

 doubtful which side is to be characterized as the back and 

 which as the belly, especially if we start from the organiza- 

 tion of the freshwater Rotatoria whose sexual organs are 

 always placed ventrally. But from the position of the mas- 

 ticatory apparatus, the ganglion, and the sexual orifice it 

 appears at once that the surface of the body regarded by me 

 as the hack really merits that name. In favour of this we 

 have also the method adopted by Paraseison in locomotion. 

 It creeps about after the fashion of a geometric caterpillar, 

 attaching itself to its support by the head, curving the neck 

 and trunk into a circle, and then attaching the caudal extre- 

 mity quite close to the head. Then the head detaches itself 

 again from the surface of support, the animal stretches itself 

 to its full length, and repeats the same movement again and 



