94 M. L. Plate on Ectoparasitio Rotatoria 



the spatuliform median laminse and are inserted upon /3 and 

 7. In the individual represented in fig. 9 these muscles 

 were contracted, bj which means the anterior extremities of 

 /3 and 7, and therefore also the denticles, were drawn apart, 

 whereas in the resting state of the muscles thej are very 

 closely approximated. Between the ossicles of the supporting 

 apparatus the efferent ducts of the ventral salivary glands 

 (fig. 9, dr') may be traced to the denticles, the action of 

 which they assist Avith their secretion. 



A little in front of the masticatory apparatus there lies 

 upon the dorsal surface of the buccal cavity a small rounded 

 body (figs. 5, 6, y), which, in the living animal, is always 

 remarkable by its yellowish-green colour. On closer exami- 

 nation this proves to be composed of several (probably four) 

 small bacilli, which are only slowly destroyed by solution of 

 potash and dilute sulphuric acid, and therefore appear to be 

 of a chitinous nature. Two of these bacilli are rather longer 

 than the others (0*016 millim.) and terminate at one end in a 

 fine, somewhat bent point. As to the significance of these 

 structures I liave been unable to arrive at any conclusion. 

 As two pyriform unicellular glands, furnished with a very 

 long efferent duct (fig. 6, dr'^), which lie dorsallj to the oeso- 

 phagus and right and left of the cerebrum, open between 

 them, they are probably functionally related to these. I 

 regard these organs, wliich likewise occur in the same way in 

 Sei'son, as viscous glands of the head, fulfilling the same 

 office as the pyriform cells of the foot. In fact, whenever a 

 Paraseison creeps about upon the object-slide, attaching itself 

 alternately by the anterior and posterior poles of the body, we 

 find at the spots where the head was fixed a shining jelly, 

 which has evidently served for the attachment of the animal, 

 and is very probably secreted by the glands above described. 

 On the other hand, two other glands (fig. 6, dr') must be 

 interpreted as salivary glands ; these, which are of the same 

 structure as those just referred to, lie ventrally to the mouth 

 and open immediately between its teeth. 



The oesopJiagus (figs. 1, 2, 6, a) forms a narrow tube, of 

 equal width throughout, which traverses the entire length of 

 the head and neck and on approaching the dorsal surface of the 

 stomach passes into it. It is formed of a delicate membrane, 

 in which I could recognize fine muscular fibres but no nuclei. 

 In opposition to most Eotatoria we find its inner wall not 

 lined with cilia, and the food taken will therefore certainly be 

 conveyed backward by a sort of peristaltic movement, as is 

 also the case, for example, in the Bynclicetm and Asplanchnce. 

 The anterior extremity of the oesophagus very often shows 



