CHAPTER XVII. 



PLATYHELMIA TEMNOCEPHALOIDEA. 



CLASS II. TEMNOCEPHALOIDEA. 



PLATYHELMIA, in which the flattened body is provided posteriorly 

 with a large ventral sucker. The epidermis is retained through- 

 out life as a nucleated syncytium, which secretes a thick cuticle, 

 but which may also carry cilia, and contain rhabdites. 



ORDER Dactylifera. 



The body is produced into finger-shaped tentacular processes along the 

 anterior margin or along the lateral margins as well ; the mouth is 

 situated anteriorly, and leads through a pharynx into a wide, nearly 

 rectangular intestine, which is without diverticula. A single genital pore 

 situated posteriorly is common both to the male and female apparatus. 



FAMILY 1. TEMNOCEPHALIDAE. With four to twelve preoral tentacles. 

 The excretory system opens to the exterior by means of a pair of anteriorly 

 and dorsally situated contractile sacs ; the vitellarium is reticulate. 

 Temnocephala, Blanch. (Fig. I. 1, 6, 7) ; Craspedella, Hasw. ; C. Spenceri, 

 Hasw., sole species, in the branchial chamber of Astacopsis bicarinatus. 

 FAMILY 2. ACTINODACTYLELLIDAE. Tentacular processes along each side 

 of the body ; a second sucker is developed in front of the mouth ; no 

 contractile sacs at the excretory pore. Actinodactylella, Hasw. (orig. 

 Actinodactylus) ; A. Blanchardi, Hasw., on Engaeus fossor (Fig. I. 3). 



Further Remarks on the Temnocephaloidea. The members of this 

 class, so far as they are known at the present day, live on the 

 outer surface of fresh-water animals, to which they attach them- 

 selves by means of the sucker ; they do not, however, feed upon 

 the "host" but on small animals, such as Entomostraca, Rotifera, 

 Infusoria, etc. ; they can therefore scarcely be termed " ecto- 

 parasites " in the usual sense of the word. Most of the species 

 occur on the surface of fresh -water Crustacea; the Brazilian 

 T. Jlieringii, Hasw., in the pulmonary chamber of the mollusc 

 Ampullaria, and T. brevicornis, Montic., on the surface of Chel- 

 onians (Hydropsis and Hydro-medusa). The genus Temnocephala 

 was discovered in Chili by Blanchard, who regarded it as an 



