The testes may be found in older larvæ or adults beneath the fifth and sixth terga of the abdomen. They lie in the fat-body, from which they are not very readily distinguished. Each testis consists of 30–40 rounded vesicles attached by short tubes to the vas deferens.[169] The wall of the testis consists of a peritoneal layer and an epithelium, which is folded inwards along transverse lines. The cells of the epithelium give rise to spermatocysts,[170] which enclose sperm cells. By division of the nuclei of the sperm cells spermatozoa are formed, which have at first nucleated heads and long tails. Subsequently the enlarged heads disappear. The spermatozoa move actively. In adult males the testes undergo atrophy, but can with care be discovered in the enveloping fat-body. [169] In _Blatta germanica_ the testes are functional throughout life. They consist of four lobes each. The vasa deferentia are much shorter than in _P. orientalis_. [170] The spermatocysts are peculiar to Insects and Amphibia. They arise by division of the spermatospores, or modified epithelial cells, and form hollow cysts, within which sperm cells (or spermatoblasts) are developed by further division. The sperm cells are usually placed radiately around the wall of the spermatocyst. They escape by dehiscence, and are transformed into spermatozoa. [Illustration: Fig. 99.--1. Male Organs, ventral view. _Ts_, testis; _VD_, vas deferens; _DE_, ductus ejaculatorius; _U_, utriculi majores; _u_, utriculi breviores. 2. Do., dorsal view, showing termination of vasa deferentia. 3. Conglobate gland, and its duct. × 8.] The vasa deferentia are about ·25 inch in length. They pass backwards from the testes, then turn downwards on each side of the large intestine, and finally curve upwards and forwards, entering the vesiculæ seminales on their dorsal side. Each vas deferens divides once or twice into branches, which immediately reunite; in the last larval stage the termination of the passage dilates into a rounded, transparent vesicle. [Illustration: Fig. 100.--Male Organs, side view. _T^7_, seventh tergum; _S^7_, seventh sternum; _Ts_, _DE_, as before. _A_, _B_, see fig. 102. × 8.] The vesiculæ seminales are simple, rounded lobes in the pupa (fig. 101), but their appearance is greatly altered in the adult by the development of two sets of utricles (modified accessory glands). The longer utricles (_utriculi majores_) open separately into the sides of the vesiculæ; nearer to the middle line are the shorter and more numerous _utriculi breviores_, which open into the fore part of the vesiculæ. The utricles form the “mushroom-shaped gland” of Huxley, which was long described as the testis. In the adult male the utricles are usually distended with spermatozoa, and of a brilliant opaque white.