179 



On the Cysticercus op T^nia microsoma and a new 

 Cysticercus prom Cyclops agilis (Rosseter). 



By T. B. Rosseter, F.R.M.S. 

 Plate X. 



(Read November IRth, 1892.J 



Cysticercus — (Rosseter) of Tcenia microsoma (Creplin). 

 Form of cyst globulous. 

 Diameter of cyst, 0'237 m.m. 

 Hooks, 10. 



Length of hooks, 0050 m.m. 

 Habitat, Cyclops agilis. 



This hitherto unknown Cysticercus (Fig. 1, PI. X.) I found 

 parasitic in Cyclops agilis, taken from a duck-pond in the 

 parish of Patrixbourne, near Canterbury. Up to the present 

 time I have only captured two specimens, and one of these had 

 evaginated itself in the perivisceral cavity of the Cyclops, the 

 connective tissue of which formed their nidus. The cuticle of 

 the cyst is devoid of striaB, neither is it fenestrated. It is 

 lined with a diaphanous epithelial layer. 



The evaginated specimen (Fig. 2) consisted of the rostrum, 

 scolex, and neck, and when dissected from the Cyclops was still 

 adherent to the cyst. 



The hooks on the rostrum (Fig. 2a) are ten in number, and 

 from the description and drawing "given by Krabbe * they 

 correspond with those of Tcenia microsoma (Creplin). Accord- 

 ing to the specimens in my possession their individual length 

 is O'OoO m.m., divisible thus : a-b 0'034, a-c 0"050. Krabbe in 

 his monograph gives them as ranging from 0*035 to 0"061 m.m. 

 — this measurement he explicitly states is after Pfaff and Olrik 

 — but in some specimens of the tapeworm taken by him from 



* See " Bidrag til Kundskab om Fuglenes Bsendelorme," p. 296, figs. 146- 

 150. 



