MisceUaneo us. 123 



by Sedgwick* for tho other Australian species. The feet closely 

 agree with those of P. nov^f-zedlandic, as hgurcd by Sedgwick (Joe. 

 cit.), being i)rovided with a dorso-median papilla above the claws 

 and a lateral one on each side. 



Jans: — The outer blade of the jaw is simple, as in P. novif- 

 zealandiif, and not provided with an accessory tootli as in P. 

 Ltnclnrtii. 



Geniliil Aperture. — The genital aperture is situated between the 

 legs of the last pair. In some specimens it is a very prominent 

 white papilla ; these are probably females. The other specimens, 

 in which it is less prominent, may be young females or males, but 

 I have found no white papilla on the base of the last leg, such as 

 exists in the males of P. Lmcl-ariil. 



Hahitat. — ilacedon, Victoria. In and upon rotten wood. 



On the Compound Eyes of Arthropods. 



' Studies from the Biological Laboratory of Johns Hopkins Uni- 

 versity,' vol. iv. no. G, contains a paper " On the Morphology of the 

 Compound Eyes of Arthropods," by Mr. Sho Watase, which is of 

 interest owing to its bearing on the origin of the compound eyes of 

 insects. 



The principal subject of tho paper is the eye of Limidus ; but 

 types of the three great groups of Arthropods — Insecta, Crustacea, 

 and Arachnids — were studied, and the results are Lncluded in the 

 generalizations at the close of the paper. 



The primitive type of tho ommatidhun, or visual unit, is traced 

 into a simple open ectodermic pit, from which he believes the com- 

 pound eyes of Arthropods to have developed by a vegetative repe- 

 tition of similar structures, not unlike what is supposed to have 

 taken place in the formation of certain compound organs in other 

 animals, such as the kidney in Vertebrates or the respiratory organs 

 in Lamollil)ranchs. 



Taking the number of facets as given by Lubbock, the compound 

 eye of the house-tly {Musca) would represent about 4000 invagina- 

 tions of the skin, and of the dragon-fly {^EscJma) about 20,000, 

 while an ocellus would represent a single pit. 



In an appendix the compound eye of the starfish is briefly con- 

 sidered, and is found to be morphologically strikingly similar to that 

 of an Arthropod. Six lithographic plates accompany the paper and 

 admirablv illustrate the author's studies. — Insect Life, vol. ii. no. 10, 

 April 1890, p. 203. 



* " ^louograph of the Species and Distribution of the Genus Peripcdim 

 (Guilding )," Quarterly Journal of Microscopical Science, April 1888. 



