319 
Notes on the Uropodinse. By A. D. Michael . 
branches communicate directly, or indirectly, with a nearly central 
point ; which probably is the point of discharge. A smaller similar 
organ is found further back, behind the insertion of the fourth leg ; 
also near the lateral edge of the dorsum, on each side, immediately 
under the cuticle ; and a whole row of pairs underlie the two nearly 
median, rough, elevated ridges on the anterior part of the dorsum ; 
these, however, are much smaller than either of the two pairs before 
mentioned. 
I cannot say with any certainty what is the function of these 
organs, but I suppose them to be dermal glands. Dermal glands are 
common in many of the Acarina ; the Hydrachnidae, as a rule, are 
particularly richly provided with them, and they are well known in 
other families ; it is true that they are usually globular or discoidal 
glands, and that I cannot point to any other known instance in the 
Acarina of the richly branched condition of the dermal glands which 
we find in the present species ; but then, as before stated, I cannot 
point to any similar organs at all in the order ; yet here they are 
present, and they appear to be glandular. Their position and dis- 
tribution seem to favour the idea that they are dermal glands. 
Expulsory vesicles , the organs to which I gave this name in the 
Oribatidae, had long been well known in the Tyroglyphidse, having 
been described by Claparede and others ; I myself have lately recorded 
their existence in some Gamasidm,* and they exist in other families ; 
but I am not aware that their presence in any of the Uropodinae has 
been hitherto ascertained. 
They are more or less flattened sacs lying near the surface in 
the lateral part of the posterior half of the abdomen ; they contain 
an oily fluid, most often yellow, and discharge to the exterior by a 
fine pore ; they are usually looked on as excretory. G. formicarise 
is provided with one of these organs on each side of the body ; it is a 
slightly flattened sac (fig. 14). and lies between the second and third 
legs just below the great raised block of dark chitin which is placed 
at the side of the median spoon-shaped depression. 
* “ On the Variations in the Internal Anatomy of the Gamasinae, &c.,” Trans. 
Linn. Soc., 2nd ser., Zool., vol. v. pt. 9 (1892) p. 311. 
