440 JOSEPH LEIDY. 



species of Trichina. In his communication on this discovery he stated 

 that this species was apparently the same as that found by Owen and 

 himself in man. The famous zoologist Leuckart, who afterward 

 worked out the life history of Trichina spiralis, acknowledged his 

 indebtedness to this observation of Dr. Leidy. In 1853 appeared the 

 " Fauna and Flora within Living Animals," a beautifully illustrated 

 and valuable work, which showed very clearly the wide range of ani- 

 mal and vegetable parasites which are to be found in the alimen- 

 tary canals of small animals, as beetles, centipedes, cockroaches, etc. 

 This paper is also interesting as having expressed ideas closely re- 

 sembling in many respects those advanced a few years later by Darwin 

 in his " Origin of Species." 



Dr. Leidy's contributions to helminthology were numerous, and of 

 such merit as to render him the highest authority on this subject in 

 this country, and the peer of such men as Leuckart, Cobbald, and 

 Diesing. His papers upon various insects and their life histories gave 

 evidence ^of his familiarity with entomology. In 1848 he made the 

 discovery of the presence of eyes in a species of Balanus, which led 

 Darwin to look for them in other members of this group. 



Dr. Leidy was particularly interested in the very lowest forms of 

 animal life. In addition to many smaller papers, he gathered together 

 in the magnificent monograph, " Fresh Water Rhizopods of North 

 America," the results of many years' study. The numerous plates 

 illustrating this volume are splendid examples of his marvellous ar- 

 tistic skill. Among the first persons in this country to use the micro- 

 scope, he early established his ability as a histologist by his valuable 

 paper, " Researches into the Comparative Structure of the Liver " 

 (1848). The views advanced in this paper, though not generally 

 accepted at the time, have since been largely confirmed by embryo- 

 logical research. 



In 1861, he published "An Elementary Text-book on Human Anat- 

 omy," in which the noteworthy attempt was made to substitute an 

 English terminology with foot-note references for the cumbersome and 

 perplexing anatomical nomenclature in common use. This was quite 

 successful, and was carried to still greater perfection in the second 

 edition of this book, which was finished a short time before his death. 

 This anatomy is unexcelled by any in the language for accuracj' of 

 detail and clearness of expression. Dr. Leidy's other papers upon 

 vertebrate anatomy exhibit the careful work and clear judgment so 

 characteristic of all that he did, and the many new facts presented by 

 him have been almost always confirmed by later investigators. No 



