356 THE EARTHWORM CHAP. 



parts of it : look for the ciliated nephrostome. (For details 

 see VI.) 



Add a little methylated spirit to the water in your dis- 

 secting dish and sketch your dissection. 



5. The ovaries. Examine segment XIII closely, being 

 very careful not to injure its contents, and the ovaries may 

 then be seen projecting backwards into this segment, one 

 on either side just in front of the crop. They can easily be 

 recognised by their shape, and by the fact that they hang 

 freely into the coelome, as can be seen by touching them 

 with a seeker. Carefully seize the septum between segments 

 XII and XIII with the small forceps, and cut around the 

 attachment of an ovary so as to remove it. Stain with 

 methyl-green or magenta, and mount in glycerine (or else 

 fix, stain, and mount in balsam, as directed on p. 136). 

 Note the mass of undifferentiated cells at the proximal, 

 attached end of the ovary, and the gradual development of 

 the ova towards the distal, narrower end. Examine the 

 ovum, and observe the nucleus, nucleolus, and granules of 

 food-yolk. Sketch the ovary. 



6. The globular spevmothectz (usually two pairs, see 

 p. 347) in segments IX X. 



III. Tease out a small portion of a sperm-sac, stain with 

 magenta, and mount in glycerine. The following stages in 

 the development of the sperms can then be made out : 

 a. the sperm-moiher-cells or gametocytes (developed in the 

 spermary) in different stages of division ; the products of 

 division, each with a nucleus, and arranged in a single 

 peripheral row, the central mass of protoplasm remaining 

 undivided ; b. the gradual elongation of these small cells ; 

 and c. the conversion of each into a sperm, the nucleus 

 forming the rod-like " head," and the protoplasm giving 

 rise to the delicate " tail " ; d. free sperms (also to be found 

 in the spermothecae ; some of them should be examined 

 fresh and their movements noted). Sketch a series of 

 stages. 



It is not easy to make a satisfactory dissection to show 

 in situ the ovaries, oviducts, and ovisacs, as well as the 

 spermaries, seminal funnels, and spermiducts ; but an 

 attempt should be made at a later stage with a worm 

 preserved in spirit (see VI.) : if possible, transverse sections 

 of the generative region, prepared as directed in C., should 

 also be examined. Note again the ovaries, and also the 

 oviducts and ovisacs, which latter can be recognised by their 

 red colour. Each seminal funnel appears something like a 



