Rudolf Leuckart. 21 



and Elasmobranch fishes. His volume ' On the Structure and Physi- 

 ology of the Honey-bee,' produced about the same time, is the best 

 treatise on the subject, and has been invaluable to scientific bee- 

 masters. 



One of Leuckart's most definite and striking discoveries was his 

 demonstration by a study of their embryology that the worm-like 

 parasites known as Linguatulidse (Pentastoma) found in the body- 

 cavity of serpents and other Vertebrata are degenerate Arthropoda, 

 probably related to the Arachnida. His me'moir on the anatomy and 

 reproduction of those remarkable Diptera, the Pupipara, is a valuable 

 contribution to the knowledge of insect morphology. His discoveries 

 in relation to parasitic worms are numerous and of great importance. 

 They are for the most part epitomised and incorporated with existing 

 knowledge in his treatise, ' Die menschlichen Parasiten,' two volumes, 

 of which the first edition appeared in 1863 and the last in 1876. Of 

 this work there is an English translation. 



He demonstrated the true nature and history of the remarkable 

 nematoid worms, Attractonema and Sphaerularia. He published in 

 1860 a separate work on Trichina spiralis, discovered originally by 

 Sir James Paget when a student in the dissecting room of Bartholo- 

 mew's Hospital, and named by Sir Kichard Owen. Leuckart gave a 

 complete history and anatomy of Trichina in its various phases of 

 growth, and assisted by his work in checking the spread of trichinosis. 

 One of his last discoveries was that of the intermediate host of the liver 

 fluke, which he showed to be the small water-snail known as Lymnceus 

 periger. In this discovery he was anticipated by a few weeks by 

 Mr. Thomas, of Oxford, now Professor in Christchurch, New Zealand, 

 who independently made the same discovery as the result of a long 

 series of experiments, and published it in this country before Leuckart 

 published his results. 



Amongst other distinguished pupils of Leuckart is Elias Mecznikow 

 the founder of the theory of phagocytosis. Mecznikow discovered 

 in Leuckart's laboratory tne extraordinary life-history of the nematoid 

 Ascaris nigrovenosa which has alternating complete sexual generations, 

 the one parasitic in the lungs of the frog and the other living in damp 

 earth. 



Leuckart has the merit of being, if not the first, yet one of the very 

 first to apply the method of "embedding" with a view to section 

 cutting to small soft-bodied Invertebrata. The method itself was first 

 devised by Samuel Strieker, of Vienna, who invented it in order to 

 facilitate his study of the embryology of the frog. The simple form of 

 embedding in wax or paraffin, which was used by these pioneers (about 

 the year 1870), has long since been developed into the modern methods 

 of impregnation with paraffin and the cutting of ribbons of sections by 

 nicely adjusted machines. 



