774 
DR JOHN RENNIE ON 
some features of interest in relation to T. ivoodi, 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 Tarsonemus as representing a transitional stage 
between the gall-forming mites, Eriophyidae or Phytoptidae, 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 
