1204 OYSTERS, AND ALL ABOUT THEM. 



such meaning, and that there are no differences between 

 the sexes except the microscopic ones. It is not necessary 

 to use the microscope in every case, however, for a little 

 experience will enable a sharp observer to recognize a ripe 

 female without the microscope. If a little of the milky 

 fluid from the ovary of a female, with ripe or nearly ripe 

 eggs, be taken upon the point of a clean, bright knife- 

 blade, and allowed to flow over it in a thin film, a sharp 

 eye can barely detect the eggs as white dots, while the 

 male fluid appears perfectly homogeneous under the same 

 circumstances, as do the contents of the ovary of an 

 immature female, or one which has finished spawning. 

 When the eggs are mixed with a drop of water, they can 

 be diffused through it without difficulty, while the male 

 fluid is more adhesive and difficult to mix with the water. 

 By these indications I was able, in nearly every case, to 

 judge of the sex of the oyster before I had made use of the 

 microscope, (b} 



Professor Huxley, in his " Anatomy of Invertebrata," 

 states that " in the common oyster the genital coaca in any 

 given individual are found to be either almost all ovigerous, 

 or almost all spermigerous, and it appears probable that 

 the predominantly male precedes the predominantly female 

 condition." 



M. Coste, speaking of the reproduction of oysters, 

 says that " the minutest researches show that, without any 

 exception, there are to be found spermatozoids and eggs 

 in the same organ, where they develop themselves side by 

 side. The capsules (or sacs) in which the spermatozoids 

 are formed arrive in the first place at maturity, and then 



(b) " The Development and Protection of the Oyster in Mary- 

 and," pp. 121-122. 



