1919] Ruckes: Male Genital System in Lepidoptera 197 



while the shorter and weaker branch (the eighth posterior) 

 extends into the body tissue. In Samia cecropia, the ninth 

 nerve arises separately from the ganglion. In Philosamia 

 cynthia, it is joined for a distance with the tenth nerve. In 

 either case, this nerve has two branches, a long anterior branch, 

 which extends caudad to the juncture of the seminal vesicles, 

 and the vasa deferentia, innervating this juncture, and forming 

 a prominent plexus there. This may be called the vesicular 

 plexus (Vp. Fig. 4). The shorter branch is homologous with 

 the shorter branches of the seventh and eighth nerves and is no 

 doubt the ninth posterior. The tenth nerve is very heavy and 

 long. It is the most interesting of all ; the strong anterior branch 

 extends caudad, to the region of the vesicular plexus, where it 

 forms a prominent loop hole, through which the vas deferens 

 passes; this nerve continues and gives rise to delicate branches 

 that form what may be called the caudal plexus (Cp. Fig. 4), 

 innervating the tissue that later becomes part of the genital 

 appendages. From each loop hole a delicate branch extends 

 entad, and unites with the vesicular plexus. The tenth posterior 

 nerve passes caudad, and supplies the same tissue that the 

 caudal plexus innervates. 



What changes take place during the transformation stages 

 have not been studied. The caudal plexus no doubt forms the 

 nerve supply for the genitalia, and the vesicular plexus probably 

 controls the muscles of the ducts. 



HISTOLOGY OF THE TESTIS. 



As previously stated, each testis consists of four chambers, or 

 testicular tubes, combined, and surrounded by a capsule. 

 Regardless of the form of a testis, from the histological aspect, 

 one may consider it as consisting of two main parts, an ecto- 

 dermal part of the sex cells themselves, and a mesodermal portion 

 comprising the follicular epithelium and the various coats that 

 make up the wall of the testis. A study of the sex cells involves 

 observations on their origin, growth, maturation and trans- 

 formation, topics that come under the heading of sperma- 

 togenesis and which are not to be treated in this paper. (Cf. 

 Pauline Dederer, Biol. Bull., Vol. 13 — Spermatogenesis in P. 

 cynthia). The author wishes to deal solely with the mesodermal 

 tissue. This may readily be considered under two headings, 



