374 THE GYPSY MOTH. 



backward for a short distance. A careful sectioning of a 

 single reproductive body shows it to be composed of fila- 

 ments, which are coiled upon each other, forming a com- 

 pact mass, which is enclosed in the external envelope. In 

 the mature caterpillar, and even in those of the fourth molt, 

 there is a marked difference in the structure of the repro- 

 ductive organs, seemingly indicative of sexual differentia- 

 tion. One form, apparently that of the female, is made up 

 of medium long, thick tubes, composed of an outer wall, a 

 thicker inner layer and a central lumen, which is enlarged 

 at intervals, and contains in these enlargements large cell- 

 like bodies surrounded by many smaller cells (nutritive 

 cells?). 



That which is apparently the male form is made up of 

 much smaller and somewhat longer tubes of a more nearly 

 even diameter. These tubes are closely coiled on each 

 other within the sac formed by the outer envelope. These 

 organs increase in size as the insect approaches the pupal 

 stage. Although our studies on the reproductive system 

 in the pupa are not yet completed, one point is well estab- 

 lished : the development of the reproductive system of the 

 future imago is accompanied by a corresponding diminu- 

 tion of the fat body with which the newly formed pupae 

 are filled. In this stage the accessory organs and glands of 

 the reproductive system are first recognizable (Fig. 5, ro). 

 The reproductive organs of the male imago (Plate 59, 

 Fig. 1) consist of a single button-shaped testis (t), formed 

 by the fusion of the two reproductive bodies of the cater- 

 pillar ; the paired seminal vessels (vs) and duct with the 

 accessory glands. Four enlargements occur on each of the 

 seminal vessels, two near the testis and two near the junc- 

 tion of the two vessels. The last enlargement has a blunt, 

 lateral projection, which receives the duct from the acces- 

 sory gland. The common duct formed by the union of the 

 two seminal vessels tapers for a considerable part of its 

 course, then enlarges to form the seminal reservoir proper 

 (sr) at the base of the penis (p), into which it discharges. 

 Around the base of the penis, and attached to the lateral 

 body walls, are bands of muscle fibre (m), which evidently 

 serve to exsert the organ. The whole system is so compli- 



