xii.] THE FRESH-WATER CRAYFISH. 147 



y. Tease out a bit of the testis in water, and ex- 

 amine with i obj. : it will be seen to be com- 

 posed of sacculated tubes. In it or in the 

 vas deferens some of the spermatozoa may be 

 found : they are motionless and have the form 

 of nucleated cells provided with radiating pro- 

 cesses. 



S. The ovary is a gland in shape and colour 

 very similar to the testis of the male. From 

 it two short oviducts arise and pass almost 

 directly downwards to the genital openings 

 (i. c. y.). 



b. Of the Lobster. 



a. The testes are two long tubes which lie partly 

 in the thorax and partly in the abdomen. 

 Their posterior portions meet in the middle 

 line, but in front they diverge, and about one 

 fourth the length of each from its anterior end 

 a short transverse branch unites the two. 



(3. The vas deferens arises a little in front of the 

 middle of each testis and passes without con- 

 volutions towards the genital opening. Its 

 distal half is dilated. 



y. Tease out a bit of the testis in water and ex- 

 amine with \ obj. for spermatozoa. They are 

 motionless, and consist of an elongated ceil 

 from one end of which three rigid pointed 

 processes radiate. 



8. The ovaries of the lobster are also elongated 

 and lie partly in the thorax and partly in the 

 abdomen, above the alimentary canal (14). 



10 2 



