body becomes as indicated above. In consequence of the inelined 
position which the spieules acquire, the number of the layers of 
spieules increases. On the average I count from 7 to 10 of these 
one above the other; here also the differently directed spines are 
thoroughly intermixed. 
The above described structure of the integument affords a suflicient 
explanation of the extreme rigidity of the specimens preserved in 
spirits, the thick euticle with the multiple layers of calcareous spi- 
cules evidently keeping the flexibility of the body within certain 
rather restricted limits. To the touch the exterior surface appears 
somewhat coarse from the points of the outer layers of spicules 
projecting to the exterior. In sections I always find it beset with 
bits of fine sand or mud adhering to it and giving to each section 
the appearance which Kor£s and DANIELSSEn mention as being es- 
pecially characteristie for their species: Solenopus incerustatus. I en- 
tertain some doubt about the specifie value of this distinction. 
The thiekness of the integument in the two specimens examined 
varies from 0.212 mm., to 0.455 mm.; the thinnest portion is the 
bridge of tegumentary tissue separating the mouth from the ven- 
tral groove: it here attains only 0.142 mm. Both at the mouth 
and at the ventral groove the layer of spicules is continued inwards 
for a very insignificant distance only; this distance is somewhat 
more considerable in the slit leading into the anterior footgland 
(fig. 28, I) at the foremost extremity of the ventral groove. 
All ihe foregoing is considerably different from what is found in 
Neomenia and moreover no bloodvessels in the integument such as 
they are figured by TuLLBERG (31, fig. 22) and were observed by myself 
in Prof. Ray LANskESTERr’s specimens of Neomenia, find their way 
into the chitinocalcareous skin of Proneomenia. ‘The mode of forma- 
tion of the spieules, which in the very beginning are small calca- 
reous bodies in the deepest cellular layers. of the integument and 
are gradualliy pushed outwards, forbids us from looking upon this 
difference in the structure of the skin as being occasioned by a 
difference in age of the speeimens. It may more probably be ad- 
mitted among the generic differences and I should not wonder if 
