450 Dr. J. D. Thomas. Taenia Echinococeus in [June 18, 



whilst in Ech. altricipariens a more or less numerous progeny of 

 daughter cysts is present. Within these, grand- daughter cysts, enclos- 

 ing a third generation, may be found. 



(6.) Kuchenmeister alleged that the Echinococeus heads in these 

 two forms, differ in the number, shape, and size of the hooklets. 

 According to him Ech. scolicipariens has twenty- eight to thirty- six 

 hooklets of somewhat blunt shape, whilst Ech. altricipariens possesses 

 between forty-six and fifty-six of more slender figure and smaller size. 



(c.) The habitat of the two forms is different, Ech. scolicipariens 

 occupying the viscera of the domestic Herbivora, whence it was also 

 called Ech. veterinorum, Ech. altricipariens, named also Ech. homi?iis, 

 being the form found in man. 



It is, however, very doubtful whether any of these differences can be 

 regarded as specific, for great variations occur in the number of 

 daughter- cysts present in Ech. altricipariens, e.g., there may be only 

 one or two small cysts, or they may be reckoned by thousands. 

 Again, as regards the characters of the hooklets, Rudolph Leuckart 

 points out that considerable variety prevails in different individuals of 

 the same species, dependent partly upon the age of the bearer, but 

 also in part upon the circumstance that the shape, arrangement, and 

 size of the hooklets are liable to considerable diversity. 



Finally, Ech. scolicipariens and Ech. altricipariens may be found 

 together in the same "host." 



Obviously, the question of the identity or otherwise of these forms 

 conld only be satisfactorily proved by experiment. If the scolices of 

 each form produced the same cestoid worm, no further doubt could 

 remain as to the specific unity of the two varieties. 



At this stage it is necessary briefly to allude to the evidence upon 

 which our knowledge of the life-cycle of Ech. veterinorum depends. 



Shortly after Kuchenmeister had initiated his helminthological 

 " Feeding Experiments " with Cysticercus pisiformis, Ccenurus, &c, 

 experiments were made to discover the cestoid form of Echinococeus 

 veterinorum. 



In 1852 von Siebold,* by a series of successful feedings demon- 

 strated that the tapeworm phase of Echinococeus was the small 

 cestoid worm, now known as Taenia echinococeus. 



The experiments of von Siebold were successfully repeated by 

 Kuchenmeister and others, and a very successful experiment was 

 also made by Mr. Edward Nettleship, in 1866, an account of which 

 was communicated to the Royal Society.f 



* " Uber die Yerwandlung der Echinococcus-Brut in Taeiiien." " Zeitschrift fur 

 "Wissenschaftliche Zoologie." Leipzig, 1853, p. 409. 



f " Notes on the Rearing of Tcenia echinococeus in the Dog from Hydatids, with 

 some Observations on the Anatomy of the Adult Worm," by Edward Nettleship, 

 Member Royal Agra. Coll., "Proceedings of the Royal Society," vol. 20, No. 86. 



