296 PROr. H G. SEELET ON SIMILITUDES OF 



Jeffreys maintained that the Cercarice found in Succinea were the 

 sexually immature representatives of the common liver-fluke 

 (Fasciola hepatica), which, I may observe, has some twenty times 

 been found infesting the human body. At the time in question 

 I maintained that Mr. Jefireys's opinion had no foundation in fact, 

 as the negative data supplied by Moulinie and Leuckart strongly 

 went to prove. It now turns out, from the experimental proofs 

 recently afibrded by Dr. Ernst Zeller, that the cercarian contents 

 oi Leucoehloridium found in Succinea attain sexual maturity in the 

 intestines of various insectivorous birds of the family Sylviadse. 

 I am indebted to Mr. Dallas for first calling my attention to this 

 discovery. (See Ann. ]N"at. Hist, for Feb. 1875, p. 146 ; from Hum- 

 bert, in Bibl. Univ., Bull. Sci. 1874, p. 366 ; also Zeller in S. & K. 

 Zeitsch. fur wiss. Zool. vol. xxiv. p. 564, 1874.) In connexion 

 with any explanation of the rapid appearance of fluke-disease 

 amongst animals in particular districts, it is especially worthy of 

 remark that the Cercarice of Distoma macrostoma pass into the 

 sexually mature condition in a few days after their change of resi- 

 dence has been effected, whilst in less than a week's time the 

 formation of ova has already commenced. 



In conclusion, I ought perhaps to apologize for having intro- 

 duced so many remarks of a practical nature into a paper other- 

 wise purely zoological ; but the supposed extreme rarity of our 

 Distoma crassum, its apparently formidable character as a human 

 guest, and the special precautions that appear to be necessary 

 against infection have together seemed to me to be a fair excuse 

 for sounding a note of warning to naturalists and others whose 

 rambles or professional duties may happen to carry them to the 

 shores of the Chinese and other eastern seas. 



Similitudes of the Bones in tbe Enaliosauria. By Haebt G-ovier 

 Seelet, E.L.S., r.G.S., Professor of Physical Geography in 

 Bedford College, London. 



[Bead March 18, 1875.] 



PAET I. 



THE RESEMBLANCES OE ICHTHTOSAURIAN BONES TO THE BONES 

 or OTHER ANIMALS. 



§ 1. The Mammalian CAar«c^er« o/" Ichthyosaurus. 



A SKULL of Ichthyosaurus could not easily be changed into that 

 of a mammal ; for though Cetaceans offer close resemblance of 



