186 EoBEKT Thompson Young, 



were found, but a few tracks were present similar to those made bj' 

 the larvae in the liver. 



A large number of methods of fixation and staining- were tried, 

 but only a few found to give satisfactory results. By far the best 

 fixative employed was Flemmes^g's strong chrom-aceto-osmic mixture. 

 The larvae were fixed in this for a period of two to three hours, 

 washed in running water for an hour and carried up thru the al- 

 cohols as usual. The next best fixative employed was a concentrated 

 solution of corrosive sublimate in 70 per cent alcohol with an 

 addition of one per cent glacial acetic acid. Use of this fixative for 

 an hour, with subsequent washing out in 70 per cent alcohol to 

 which was added a few drops of iodine solution, gave good results. 

 Heedenhain's iron alum haematoxylin, sometimes employed with no 

 counter-stain, but more often counter-stained with eosin, Bordeaux 

 red, or saturated aqueous solution of wasserblau and picric acid is 

 the stain which gave the best results. Vom Rath's solution followed 

 by pyroligneous acid, as recommended by Tower (1896) was 

 thoroughly tried and some good preparations of nerves and par- 

 enchyma obtained by it. but in general the results from this method 

 are not as satisfactory as those from Heidenhain's haematoxylin. 

 Apathy's foregilding with gold chloride, Golgi's rapid method and 

 the methylen-blue method were all tried. The first method proved 

 an utter failure, the second gave some good impregnations of the 

 excretorj^ ducts, while with the last some good stains of "myoblasts" 

 and their connected muscle fibres were obtained. None of them, 

 however, gave a satisfactory preparation of the nervous system or 

 sense cells. 



3. Histogenesis. 



a) Earlier Stages of Development. 



The larvae occur in the liver usually in groups of three or 

 four enclosed in fibrous cysts composed of modified liver tissue. 

 Tho many small larvae have been examined, some of which did not 

 exceed 40 f^i in diameter, none have yet been found on which the 

 embryonal hooks were present. The larvae are at first usually 

 collected in groups of a few to every cyst. As they leave the cysts 

 to wander out of the liver, they are found singly. In the earliest 

 stages observed in the liver they consist of a simple mass of loose 



