FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 137 
fold back upon the head, forming the main expansion of the insectean 
head is [are] apparently the tergum of the antennary segment,’ — a 
statement unsubstantiated by later and more extensive studies. 
The only account of the formation of the mouth-folds of Collembola is 
by Miss Claypole, who also studied Anurida maritima, giving her results 
briefly in 1896 and finally in 1898. The following extracts from her 
valuable paper (98, pp. 264-266) summarize her observations and 
conclusions: “On each side of these [three pairs of mouth-parts, as in 
my Stage 3] has appeared a ridge that passes backward along the embryo, 
the two folds enclosing the mandibles and maxillz. These folds start 
from just the region where the small intercalary appendages were seen 
earlier, but which have now disappeared. Figures 43, 46, and 47 show 
the process by which this change takes place, and leave no doubt that 
the folds, as they finally appear, are a development from the intercalary 
appendages. . . . The labrum in front and these lateral. folds make 
together a three-sided box in which the mouth-parts, two mandibles, and 
four maxille are sheltered. . . . The second pair of maxille has been 
modified to form the back of this pouch.” The author (pp. 265-266), 
after homologizing the neuromeres of Orthoptera and Crustacea, draws 
the important conclusion that the mouth-folds of Anurida “ including 
without doubt its allied forms,” are “clearly homologous with the second 
antennee ” of Crustacea. 
I quite disagree with this author as to the origin, and consequently 
the homology, of the mouth-folds. A priori arguments are here super- 
fluous, as the question is one of fact. As I have shown, the folds begin 
on, or very near, the mandibular segment, but always outside the paired 
fundaments of the mouth-parts, and never at the premandibular append- 
ages. The folds eventually and necessarily involve the intercalary region 
on progressing towards the labrum, although previously their early indi- 
cated continuity with the second maxille (Plate 2, Figure 10) is estab- 
lished. Conceptions as to the development of the fold are of course but 
inferences from facts observed in certain stages. The most apparent 
inference from the figures cited by Miss Claypole as leaving no doubt 
about the accuracy of her conclusion is certainly the one she has drawn ; 
but from the same figures and from her preparations — which Miss 
Claypole has most kindly lent me— may also be drawn the less ap- 
parent, though I believe correct, inference that the folds begin between 
the interealary and second maxillary regions and grow towards both of 
them. I have found stages intermediate between those shown by Miss 
Claypole in Figures 46 and 47, which convince me that this is the 
