122 
Sarcoptes 
the tocostome or orifice by which they discharge the eggs to the exterior; at 
their point of union there is a lubricating gland. Gudden’s results must have 
been due to pure dissection without the aid of the microtome, and are nothing 
less than astounding. 1 have made no attempt so far to investigate the internal 
anatomy of Sarcoptes, and I only find myself in disagreement with Gudden on 
one point; he figures the copulatory duct or vagina as a fine tube of even 
calibre passing from the copulatory papilla to the spermatheca; I find that it 
widens gradually and that this is the case in every specimen examined. 
Gudden’s other results I accept with all humility. A year before the publica¬ 
tion of Gudden’s work the papilla had been seen and figured by Robin (1860); 
unfortunately he regarded it as a median spine, similar to the other noto- 
gastric spines except for its smaller size. On the whole Gudden’s discovery 
has received very little attention though it is quoted in Railliet’s text-book 
(1895). Megnin (a) copies one of Robin’s figures which show the papilla as a 
spine, though he makes no acknowledgement of the source of the figure and 
(1886) states that “les Glyciphages sont les premiers acariens chez lesquels 
nous constatons l’existence d’un organe speciale de copulation; chez les autres 
Sarcoptides, la copulation se fait par le fente anale, comme nous avons 
maintes fois constate.” Trouessart (1893) corrects this error, and says that 
his own observations support Gudden; he states that the male copulates with 
the immature female, and that it is in this stage that one best sees “ la poche 
copulatrice”; the opening of the “poche,” or as I should call it the papilla, 
looks like a hair-base from which the hair has been broken, but it is unpaired 
and median; the papilla is always referred to as being behind the anus, a mis¬ 
interpretation which we must account for by supposing that in compressing 
specimens for microscopic examination the anus was brought round to the 
ventral surface. Munro (1919) and Warburton (1920) make no reference to 
the papilla nor to the discrepancy between Megnin’s views and the facts of 
the case; it appears that they overlooked the papers of Gudden (1861) and 
Robin (1860). 
The anus (an) is a longitudinal slit at the extreme end of the body; it 
extends slightly more on the dorsal surface than on the ventral which is inter¬ 
esting because in the closely allied genera Notoedres and Prosopodectes it is 
distinctly dorsal imposition. The anus is bounded on each side by a straight* 
thick lip. Fiirstenberg figures the anus of various species of Sarcoptes not as 
a straight slit, but with a concavity towards one side or the other. This at any 
rate so far as S. scabiei var. equi is concerned is an error, produced probably by 
the study of slightly compressed specimens. Fiirstenberg was on the whole a 
most careful man, but it is important to correct his errors because his figures 
have been reproduced widely. Robin (1860) and Railliet (1895) figure and 
describe it correctly. 
