314 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 
of specimen of specimen 
a 
Amphioxes 
dermal gastral | choanosomal dermal gastral choanosomal 
Length limits mm. 0.56-1.7 0.6-1.9 0.7-2.6 0.5-1.6 0.46-1.8 | 0.75-2.8 
thickness limits yu 11-32 0.45 8-30 12-34 7-59 8-29 
Relative . a 
limits 28-120 24-150 58-173 23-87 22-91 83-137 
length 
(length: 
thickness = average 66.9 59.6 116.8 63.2 44.3 103.3 
10000 :) 
“Lransvetee Gitieter On alae 1-50 | 1433 | 1442 9-60 11-32 
central tyle, limits | 
SS SSS SSS SS Se el 
The tyle exceeds the | | | 
adideent sparisicheene 2-6 iio. | 268 7). Seete Be en i = 
spicule in thickness, by 
(limits) yu 
| 
bent amphioxes usually enclose an angle of 130°-140°. Their bend is generally 
situated so much nearer one end than the other that one limb is six to eight 
times as long as the other, the spicule consequently having the appearance of a 
promonaen. Rarely the bend lies in the middle. The tyle is, as stated above, 
generally only 1-6 » thicker than the adjacent parts of the spicule, and in that 
case simply oval. Occasionally, however, much stouter tyles are observed, 
and in these cases it is clearly to be seen that the tyle is composed of from 
one to four rounded knobs representing rudimentary rays. A few spicules 
of this kind were triactine, a perfectly developed ray occupying the place of one 
of the knobs. Such triactines were observed both among the superficial and the 
choanosomal amphioxes. 
The proportion of length to thickness is in-the choanosomal amphioxes 
of both specimens together 10000 to 58-173, on an average 10000 : 109.3. 
As the curve 
(Fig. 17), in which the reciprocal proportions (thick- 
ness < 10000: length) are represented, shows, there is no great difference 
in the average relative thickness of the smaller and the larger choanosomal 
amphioxes. 
In the superficial (dermal and gastral) amphioxes (Plate 82, figs. 13-19) the 
proportion of length to thickness is 10000 to 74-447, on an average 10000 : 
241.3. Among these the shorter are, on the whole, as the following table shows, 
relatively much thicker than the longer. 
