7 
did not the strings of connective tissue keep up a direct commu- 
nication with the layer in which all the spicules originate (fig. 23,1). 
Simultaneously with the‘ growth in thickness of the interspicular 
substance the connecting string thus increases in length. 
The spieules such as are found in Neomenia (TULLBERG , v. GRAFF) 
and the intermediate stages between these and the simpler needle 
forms are absent in Proneomenia sluiteri, which moreover wants 
the dorsal keel from which Neomenia carinata takes its name. All 
the spicules are elongated cones, blunily truncated at one end, 
pointed at the other. 'The truncated end is well visible in sec- 
tions; isolated spines generally appear more rounded at the poste- 
rior extremity. Several spicules are moreover very slightly bent. 
The average size is 0.2 mm., the thickness varies from 0.018 to 
0.02 mm. (fig. 5). Looked at from above the spicules all along 
the surface of the animal are seen to be arranged in two sets, 
everywhere intermingling and placed at about right angles to each 
other (fig. 6). Neither of these sets has its spicules in the same 
direction as the body-axis, both of them make an angle of about 
45° with the latter and have their points directed backwards, to- 
wards the posterior extremity of the animal. 
Sections show that the position of the spicules in the chitinous 
euticle differs according to the body region examined. Where the 
integument folds round into the longitudinal groove, all along the 
median line of the ventral surface and also on the head, the spi- 
cules are situated more or less strietly radially, or at least perpen- 
dicular to the exterior surface; here also there are generally not 
more than two layers of spieules, the one situated lower down, 
the other about half way in the chitinous cuticle (fig. 24, I), the 
individual spieules alternating. Proceeding more towards the sides 
of the body as well as all over the back we find that the spicules 
change their position: they no longer remain directed vertically 
towards the body surface but are on the contrary more or less 
inclined, generally even very much so, those in the deeper layers 
of the integument not excepted (ig. 23, DJ. At the same time 
the direction of their longitudinal axis wilh respect to that of the 
