252 ENTOZOA. 



as incorrect in viewing tliem as cutaneous glands " secreting a 

 mucus destined to lubricate the surface of the body." 



To offer a true explanation of their character and purpose is 

 still, however, a matter of great difficulty ; for there seems to be 

 no doubt that in some instances, especially in mature cestodes and 

 in certain trematodes, the presence of carbonate of lime is contra- 

 indicated. The circumstance also of Claparede's having discovered 

 these bodies to be included within dilatations or coecal pouches 

 connected with the excretory system of Holostomata, considered in 

 association with the fact that I have myself found them lodged in 

 peculiar oviform sacs in Tricuspidaria (Triasnophorus) , would like- 

 wise seem to forbid our acceptance of Yon Siebold's notion, that 

 the bodies in question are comparable with the " spicules and 

 calcareous networks" strengthening the integument of Echino- 

 derms. JSTevertheless, this generally-received notion of a cutaneous 

 skeleton seems more readily acceptable than the philosophical 

 opinion entertained by Huxley, who regards these so-called cal- 

 careous corpuscles as homologically identical with the thread-cells 

 of the hydroid polyps. 



