542 W. WOODLAND. 
crowding of the spicules one upon the other, and the 
presence of free scleroblasts and multitudinous elongated 
cells (‘‘ fibres”), quite defeats any such endeavour; it is 
only possible to say that in young Cucumariide of the 
size above mentioned perforated plates of two, three, or more 
concentric series of perforations possess a very variable 
number of scleroblasts (I have rarely counted more than a 
score), quite irregularly arranged with respect to the form of 
the spicule, and differently arranged in different cases. 
The criticism may be made that all the irregularity in dis- 
position and number of the scleroblasts I have above insisted 
upon is due to disarrangement involved in preparation of the 
body-wall, and that in reality scleroblastic spicule-formation 
in Cucumariide proceeds after the beautifully symmetrical 
fashion described with so much assurance by M. Hérouard.! 
Such a criticism will have but little weight with those who 
observe the actual facts, since, for one thing, the body-wall 
and its contained spicules show no signs of disturbance, and 
this is very easy to detect when such has occurred (as at the 
extreme edges of portions of the wall which the observer of 
course avoids). Moreover, the body-wall, by my methods of 
preparation, is never subjected to rough treatment. The 
internal muscular layers separate quite easily from the 
hypostroma of the wall, and if each Cucumarian body-wall 
be cut into eight or more portions with a sharp scalpel, there 
is no need to subject these to any sort of tension in order to 
flatten them out on the surface of the slide. 
In the foregoing I have given an account of the early 
scleroblastic development of the commonest type of spicule 
(z) to be found in C. sp. In the case of the knobbed (a), 
and the large irregular small-holed (c), varieties of spicule 
1 Tt is hardly necessary to point out that such a version of scleroblastic 
spicule-formation as that of Hérouard involves considerably more obstacles in 
the way of explanations than the truth. How does M. Hérouard account 
e. g. for the simultaneous arrival of the four eells forming a detachment, and, 
still more, their symmetrical disposition about the spicule when they have 
arrived ? 
