HYALONEMA (PRIONEMA) PINULIFUSUM. 289 
1.1 times longer than the next smallest. This point lies between 62 and 84 u. 
The amphidises 62 » long and shorter, that is those 15-62 u in length, I consider 
as micramphidises. Some of these micramphidises have relatively longer, others 
relatively shorter anchors. The relatively long-anchored are 15-35 u long, the 
relatively short-anchored 33.5-62 ». The length frequency-curve of the micram- 
phidises exhibits two marked principal elevations which correspond respectively 
to the most frequent sizes of the long- and short-anchored forms. Within the 
micramphidiscs two groups can therefore be distinguished, both from a mor- 
phological and biometrical point of view: — smaller long-anchored micramphi- 
discs, and larger short-anchored micramphidiscs. 
Of the amphidiscs 84 « long and longer, that is those 84-470 yu in length, 
some have slender, others broad anchors. The slender-anchored are 84-380 yu 
long, the broad-anchored 370-470 u. The part of the length frequency-curve 
pertaining to these amphidiscs exhibits one pronounced main elevation situated 
at about 425 yu, close to its maximum end. The amphidises represented by this 
main elevation are all broad-anchored. These spicules form a homogeneous 
group, which I name macramphidisc because it comprises the largest amphidises 
of the whole series. Some of the slender-anchored amphidises have smooth, 
others serrated teeth. Those with smooth teeth are 84-292 u long, those with 
serrated teeth 214-380 ». Since the slender-anchored amphidises with serrated 
teeth are on the whole much larger than those with smooth teeth; since all the 
slender-rayed amphidises over 292 u in length are serrated ones; and since the 
morphological difference of teeth serrated and teeth smooth is of considerable 
importance, I propose to consider these two kinds of slender-anchored amphidises 
as belonging to two distinct groups; although biometrically, judged merely by 
the length frequency-curve of the amphidises in general, they are not differen- 
tiated. I name these two groups, which are, in size, intermediate between the 
micramphidises and the macramphidises, smooth mesamphidiscs and serrated 
mesamphidiscs respectively. The length frequency-curve of each exhibits, 
when taken by itself, a depression, particularly well-marked in the case of the 
curve of the latter. In the curve of the smooth mesamphidises this depression 
lies at 121 u, in the curve of the serrated mesamphidises at 260 4. As shown 
by the two depressions of these two curves, a large and a small kind of spicule 
can be distinguished in both of them. 
The amphidiscs of Hyalonema (Prionema) pinulifusum can accordingly be 
arranged in seven groups: — 
