FOLSOM: MOUTH-PAETS OF ANURIDA MAKITIMA. 137 



fold back upon the head, forming the main expansion of the insecteau 

 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. 264-206) 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, 

 tue two folds enclosing the mandibles and maxillte. These folds start 

 from just the region whei-e 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 thi'ee-sided box in which the mouth-parts, two mandibles, and 

 four maxillae are sheltered. . . . The second pair of maxillse 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 

 anteunse " of Crustacea. 



I quite disagi-ee 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 maxillae (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, tliough I believe correct, inference that the folds begin between 

 the intercalary and second maxillarj^ 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 



