INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 42 1 



cent, spirit, and removing the capsule of the testis ; tliey exhibit 

 various degrees of aggregation in the different forms. In Lyccena, a 

 median constriction of the capsule alone serves to indicate externally 

 the connection with the paired type of organs : the eight tubes within it 

 are arranged fan-like, four on each side. In Argynnis selene the tubes 

 are packed like the segments of an orange; in several species the 

 tubes of one side are wound round those of the other side. Pygcera 

 anachoreta and Aglia tau are now shown to have two testes. 



The Lepidoptera are thus arranged according to these cha- 

 racters : — 



Type 1. With two compound testes (the fundamental type) — 

 Hepialus. 

 „ 2. With two apparently simple testes — Pygcera anachoreta, 



&c. 

 „ 3. With one testis, the capsule medially constricted — e.g. 



Lyccena cegon. 

 „ 4. With one unpaired testis — Pieris, Vanessa, Argynnis, &e. 

 All these forms are closely connected by their internal structure, 

 inasmuch as either in the larva) or in the embryo, each vas deferens 

 is connected with four tubes. The external capsule may be wanting, 

 and has a connection with the testes analogous to that of the 

 scrotum in Vertebrata. 



Thorax of the Blow-fly.* — The object of this paper (by Mr. A. 

 Hammond) is to determine the limits of the several segments of 

 which the connate thorax of the Diptera, as exemplified in the blow- 

 fly, is composed. 



After introductory remarks on the present state of our knowledge 

 as to the constituent parts of the thoracic segment of the Insccta, the 

 author describes in detail the several pieces of which the thorax of 

 the blow-fly is made up, as they are presented from different points 

 of view, noticing the iuter2)retation put upon each of these pieces by 

 previous observers, especially Burmeister and Lowne. Evidence 

 derived from three separate sources is adduced to show, first, that the 

 posterior vertical wall of the thorax, described as mctathoracic by 

 these two authors, is really the postscutellar region of the mesothorax 

 greatly developed ; all tliat remains consequently of the metathorax 

 being reduced to the haltercs, the entostomum, and the posterior coxa) 

 and legs ; secondly, that the prominent anterior angles of the dorsum, 

 called humeri, and described by Burmeister as his pi'onotum, are 

 correctly so described, being the homologues of the posterior angle of 

 the collar of the Ilyraenoptera. 



The tlirco convergent lines of reasoning brought to bear upon 

 tliese jKiints arc : — 



1. The analogy presented by other insects. 



2. The evidence from devidopniental cliange. 



3. Tliat obtainable from the nervous and muscular systems. 



By tlie first of these a relation is souglit to be established between 

 th(! development of the meso- and metathorax in tlie three associated 



* '.Tourn. Linn. Soc. (Mot.)," xv. (ISSO) p. ".». 



