280 CLA YPOLE. [VoL. XIV. 
Respiratory System.— Anurida, as has long been known, 
lacks entirely any tracheal system; respiration is carried on 
wholly by means of the skin. In the embryos no invaginations 
were seen to represent even the rudiments of such a system. 
There are, however, at the bases of the legs and at different 
parts of the abdomen large unicellular glands that may have 
some relations to tracheal openings or the different glands 
found in myriapods and other Tracheata. This point, too, 
remains for further investigation. 
In conclusion I wish to acknowledge the helpful oversight 
given to me during this investigation by the Department of 
Zodlogy of the University of Chicago, where the greater part 
of the work was done. My thanks are especially due to Dr. 
W. M. Wheeler, under whose direct supervision the subject 
was undertaken. I am also indebted to him for many valuable 
suggestions in the treatment of the subject and in methods and 
much assistance in reaching literature, and I wish here to 
express my grateful appreciation of the aid so freely given. 
Since finishing this article, two contributions have been 
made to our knowledge of the development of the Apterygota, 
in both cases of the Thysanura. One article is by Dr. Heinrich 
Uzel, in the Zoologischer Anzeiger (Bd. XX, Nrs. 528, 529, and 
535) for 1897, entitled “ Beitrage zur Entwicklung der Thy- 
sanuren” (Campodea staphylinus Westw. and Lepisma saccha- 
vina L.). Another is by Dr. R. Heymons, published in the 
Zeitschrift fiir wissenschaftliche Zoologie for 1897, on the 
subject of “ Entwicklungsgeschichtliche Untersuchungen an 
Lepisma saccharina, L.” There are many points of interest 
between the observations made by these authors on the Thy- 
sanura and those given above for Anurida; one or two in 
particular will be briefly mentioned. 
Both authors describe the cleavage as distinctly superficial 
in Lepisma, and Uzel observes the same to be true in the 
spherical egg of Campodea. This is an interesting point in 
