Il6 NATHAN FASTEN. 



passed through the various grades of alcohol, being left in each 

 for about ten hours, and after being cleared in xylol was finally 

 mounted in balsam. 



Many mature males, females, and copulating individuals were 

 also imbedded in paraffine for sectioning. These were cut into 

 frontal, sagittal and transverse sections, ranging from 3-6 ju in 

 thickness, and stained either in Delafield's haematoxylin and 

 eosin or in Heidenhain's iron-alum haematoxylin and acid fuchsin. 

 The latter stains gave the finest results and were utilized almost 

 exclusively. 



THE MALE REPRODUCTIVE ORGANS. 



The male reproductive organs of Lernceopoda edwardsii are, in 

 the main, similar to those of the free living copepods, as described 

 by Gruber (1879). They are paired, and are located in the 

 posterior half of the body (Figs. 1-2, /., v.d., and sp.). These 

 organs lie in the space between the intestine and the lateral body 

 wall, and consist of three main parts: (a) the testis (Figs. 1-2, /), 

 (b) the coiled vas deferens (v.d.), and (c) the spermatophores 

 (sp.). The testis is sac-like in appearance, with its anterior end 

 projecting into a tube-like structure that ends blindly. When a 

 section of the testis is examined under the microscope, three 

 distinct zones can be recognized which correspond very closely 

 to the three zones in the testis of Diaptomus sp., described by 

 Ishikawa (1891). The anterior portion is the formative zone, 

 and consists of spermatogonial stages. The middle region is the 

 zone of growing spermatogonial cells, and lastly, the posterior 

 region represents the maturation zone. Here the testis is in 

 active proliferation and is filled with great numbers of sperma- 

 tozoa. Each testis unites with the vas deferens posteriorly. 



The vas deferens is an elongated coiled structure composed of 

 three parts. The first portion of the vas deferens (Figs. 3-4, 

 v.d. i), lies nearest the lateral body wall of the copepod, and re- 

 ceives the spermatozoa from the testis. The second branch 

 (v.d. 2), is a thin, tube-like structure that makes its way from the 

 lower margin of the preceding portion (v.d. i) and then coils up 

 diagonally behind it, to a point slightly above the terminal region 

 of the testis. This is best seen in Fig. 4. It then coils forward 

 as the third lobe of the vas deferens (v.d. j). This runs along 



