V PRACTICAL DIRECTIONS 343 



coiled tube, plentifully supplied with blood-vessels, and that long 

 vibratile cilia can be seen in parts of it. (For details see § VI). 



Adda little methylated spirit to the water in your dissecting 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 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, at- 

 tached end of the ovar)', and the gradual development of the ova 

 towards the distal, narrower end. Examine an ovum, and observe the 

 nucleus, nucleolus, and granules of food-yolk. Sketch the ovary. 

 •'•(The oviducts and ovisacs are not easy to make out in dissec- 

 tions). 



6. The globular spermothecce (usually two pairs) in segments IX 

 and 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 spenii-mother-cells {AtYt\- 

 oped in the spermary) in different stages of division : the products of 

 division, each with a nucleus, become 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 proto- 

 plasm giving rise to the delicate "tail." d. Free sperms (also to be 

 found in the spermotheca^). Sketch a series of stages. 



It is difficult to make out the two pairs of spermaries and the 

 spermiducts by dissection, and they can be more easily studied by 

 examining transverse sections, prepared as directed below. (In Lum- 

 bricus the spermaries and seminal funnels are enclosed within the 

 median sperm-reservoirs.) The spermiducts are partly embedded in the 

 body-wall. 



IV. Remove the sperm-sacs carefully, and make out further details 

 as regards the enteric canal (see § II. 2). Note the cesofhageal glands. 



