100 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



In order to obtain them and fertilize them artificially, 

 open a number of fresh specimens by cutting across the 

 middle of the shell horizontally with a strong knife. 

 Notice that the reproductive organs of some of them, the 

 females, are dark brown, while those of others, the males, 

 are milky white. After two or three of each sex have 

 been opened, cut out a small fragment of the ovary of a 

 female, and place it on a glass slide, with a drop of watt T, 

 and pressing and moving it gently, notice that the minute 

 brown eggs escape into the water. After these have been 

 shaken out of the fragment throw it away, and examine 

 the drop under the microscope with a power of fifty to 

 one hundred diameters, noticing the dark, brownish-red, 

 spherical yolks, with their thick, transparent shells. If 

 the eggs are of uniform size and color, they are probably 

 ripe, and ready for fertilization ; but if they vary much 

 in size, and if some are more transparent than others, 

 other specimens should be examined until one is found in 

 which the eggs are more uniform. Place this specimen 

 on one side, where it can be recognized, and keep it until 

 a ripe male is found. 



Cut a small fragment from the white testis of a male, 

 and tear it to pieces in a drop of water, and examine, with 

 a power of about one hundred diameters, the white fluid 

 which escapes. It will be found to consist, in great 

 part, of minute granules, which can barely be recognized 

 with this power. These particles, which are the sperma- 

 tozoa, will be seen to be in constant dancing or jerking 

 motion. It is rather difficult for a beginner to determine 

 whether the spermatozoa are fully ripe or not. The best 

 plan is to examine fluid from several males, and to set 

 aside the one in which they are most uniform in size and 

 active in motion. 



