212 DR JOHN RENNIE ON 



some features of interest in relation to T. woodi, and it seems worth while con- 

 sidering these in some detail. Dahl has described a species termed by him 

 T. hominis, which was obtained by E. Saul, the female from a fibroma of the human 

 ovary, and the male from a carcinoma of the same organ. Later in the same year, 

 Saul published micro-photographs of T. hominis and of others obtained from a 

 cancer of the mouse, a papilloma of a horse, and a sarcoma of a dog. Following 

 the publication of Saul's photographs, Blanc and Rollet (1910) published a state- 

 ment that they had in their possession an acarid obtained in 1909 from the urine 

 of a patient suffering from a refractory cystitis. They describe the specimen in 

 detail and recognise it as a male of T. hominis. 



T. hominis is distinguished, according to Dahl, from all previously described 

 species by the following. In the female the fourth pair of legs is more shortened 

 than in other species. Except for the end bristles it does not reach to the hinder 

 end of the body. The third pair has a longer, thinner, two-segmented end part sharply 

 marked off from the basal segment by the greater width of the latter. The two 

 bristles at the hind end of the body are wider apart than is the case in other species. 

 The male is distinguished from all other known males by the size and • thickness of 

 the long bristle at the end of the last pair of legs, and by the presence of a thick, 

 club-shaped appendage on the second pair of legs (riech-haar of Oudemans). 

 Both sexes are further differentiated by the course of the epimeral grooves on the 

 posterior ventral surface. 



Dahl groups all the forms from mouse, horse, and dog tumours as T. sauli. 

 Amongst these there are two males, distinguished from T. hominis in that, of the 

 five longitudinal furrows, the three innermost are united by a well-developed trans- 

 verse furrow, and the sensory organ on the second pair of legs is not more developed 

 than in the first pair. In the females constant distinguishing characters could not 

 be made out. He states that the same difficulty applies to the females from gall- 

 inhabiting species. 



Mr Stanley Hirst has kindly directed my attention to the fact that the con- 

 clusions of Dahl have been severely criticised by Reuter (1910) both as regards 

 the probable accidental introduction of the mites in question to the preserved tissues 

 from which the preparations were made, and as to the identity of the species. It 

 appears to me that Dahl has not shown sufficient care in differentiating the forms 

 found from species already described. 



Affinities of Tarsonemus woodi, n. sp, 



Dahl (1910) regards the genus Tarsonem,us as repi'esenting a transitional stage 

 between the gall-forming mites, Eriophyidse or Phytoptidse, and other mite families. 

 He bases his conclusions largely upon the characters of the fourth pair of legs. In 

 the species which are not endoparasitic in animals, but lead a life in relatively free 

 space and where mating may be effected in the open, the fourth pair of legs in the 



