lO WRIGHT AND MACALLUM. ' [Vol. I. 



with by chance in a small aquarium. No note was made of 

 tactile hairs during the observation of the living Sporocyst, nor 

 are such to be detected in a series of sections prepared from it, 

 although the papillse themselves are well-preserved. The latter 

 will probably soon be described by Prof. Leuckart, to whom the 

 series was transferred on account of its exceptional interest, 

 and to whom the senior author is much indebted for kind 

 assistance in the study of the anatomy of the Trematodes and 

 Cestodes. 



In connection with the above it may be recalled that various 

 marine Cercariae have been described with bunches of setae 

 {Cercaria setifera, Miiller)^, and it is extremely probable that all 

 the structures referred to belong to the same category. 



The tactile cones of Sphyranura are especially numerous 

 on the upper lip, where they must have an abundant nerve 

 supply from the plexus, to be afterwards, described in that 

 region. 



Nothing remains to be stated as to the investing membrane 

 except that certain of the parenchymatous muscles are attached 

 to its deep surface, Figs. 2 and lo, which produces in many 

 specimens a slight irregularity of its inner contour. In a speci- 

 men which has been subjected to examination for some time, 

 and is in a moribund condition, certain protrusions of the 

 investing membrane are brought about by the accumulation of 

 fluid in the subjacent space. Such protrusions are apt to take 

 a rounded outline, and are seen on examination to be bounded 

 on either side by a muscular attachment ; these, therefore, tie 

 down the investing membrane, which would otherwise be lifted 

 off by the osmotic process. 



The Organs of Attachment. 



In describing the general appearance of Sphyranura we have 

 made reference to the obstinacy with which it can attach itself 

 to any surface ; this is rendered possible by the hooks and 

 suckers borne on the ventral surface of the caudal lamina. 

 Bearing in mind the development of Polystomum we shall first 

 describe the hooks as phyletically the older organs. As in 

 Polystomum, Gyrodactylus, and Dactylogyrus two of the 



'Fewkes, Amer. Jour. Sci., Feb., '82. 



