249 
mass is present. Bieler has called attention to the fact that this peculiar 
type of cement gland is distinctive for the family Neoechinorhynchidae 
and has discovered that eight giant nuclei are always present in the 
cement gland of N.agilis. The last statement has been corroborated by 
the observations of the present writer. 
Stossich was in error in regard to the number of circles of hooks 
upon the proboscis. It seems probable that this error resulted from his 
basing his description upon the study of a poorly executed drawing (see 
Fig. 41, Pl. XXVIII) in which the hooks of the terminal circle were so 
grossly distorted that they have the appearance of belonging to two 
entirely distinct circles. Notwithstanding the fact that Porta (1905 : 213) 
in the explanation of his plate indicates that Figure 12 of N. agilis is 
original, it bears a striking likeness (see Fig. 40, Pl. XXVIII) to the 
figure given by Stossich (1885). The peculiar misrepresentation of the 
hooks and of their arrangement is identically the same in the two figures. 
The two hooks of the terminal circles seen in profile appear to be of an 
entirely different order from the remaining hooks of that circle, which 
are much distorted through foreshortening. As a consequence of this 
error in observation Porta (1905 : 166) was induced to consider Echino- 
rhynchus hexacanthus Dujardin as a synonym of N. agilis, believing the 
species to be greatly variable not only in regard to the dimensions of the 
hooks, but with reference to the number of hooks as well. In spite of 
this belief, his own description of N. agilis ignores the extent of this vari- 
ability and includes but a single measurement for each type of hooks. 
The present writer, after examining hundreds of specimens belong- 
ing to four different species of Neoechinorhynchus, has failed to find a 
single individual deviating from the typical arrangement of three circles 
bearing six hooks each. In Porta’s description his “armata di 15-18 uncini 
disposti in 3-4 serie.’”’, implies a variation which would necessitate a 
revision of the original description of the species, since even as early a 
worker as Rudolphi included in his description of the species a statement 
of the constant relations of these hooks. Porta’s statement, involving a 
radical departure from the observations of other workers in the field, 
must inevitably be regarded as problematical in the highest degree. 
VARIABILITY IN NV. agilis 
As shown in Table IV, Hamann has given a measurement for the 
terminal hooks of N.agilis more than twice that given by Porta, yet 
neither writer has given any attention to the range of variability in the 
size of the hooks. It is not impossible that Porta considered only the pro- 
truding portions rather than the entire hooks, but even on this assump- 
tion his descriptions and his drawings can not be made to agree. Accord- 
ing to his text, hooks of the basal circle are less than half the length of 
those in the middle circle; yet his figure shows practically no difference 
in the lengths of these two types of hooks. 
In considering the range of variability of the proboscis hooks for any 
species of Acanthocephala the mechanical difficulties involved in obtain- 
