16 * D. MOORE ON THE GENERATIVE PROCESSES 



the presence of immature spermatozoa to the young animal ready to be set free 

 from its parent. 



The necessity of getting many objects into a small space has obliged me to 

 alter the figures slightly from the original camera lucida drawings, so that al- 

 though there is some approach to micrometric exactness, the magnification given 

 may be taken rather as an indication as to what may be seen with certain mag- 

 nifying powers than as exact results of careful measurement. About 100 

 diameters, or about 250 diameters, &c, would be a more truthful statement than 

 X 100, X 250, taken literally. 



Cardium edule. 



Fig. 1. — A shows a lobule of the generative gland containing immature sperm 

 cells. B is a highly magnified perfect spermatozoon. 



2. — A shows a lobule slightly compressed in the compressorium, the 

 spermatozoa being nearly all squeezed out ; clear cells are seen remaining. B is 

 a small quantity of the expressed spermatozoa and clear cells from the above, 

 and C shows what I believe to be the act of impregnation in the cockle by the 

 entrance of a spermatozoon into a clear pellucid cell, which I take to be a germinal 

 vescicle. The extremely rapid lashing motion of the spermatozoon after its 

 entrance into the cell is very remarkable, and continues unabated long after 

 surrounding spermatozoa, which have not penetrated, are still. After some 

 hours of movement the spermatozoon seemed to fade, if I may so express it. 



3. — A, shows a lobule filled with eggs ; the attachment of the lobule to the 

 tube is shown. B, Some eggs, showing the micropyle well. This, I may 

 mention, is more easily seen after staining with carmine. 



4. — A is a branched portion of ovarian tubing. 



B, a yelk ball. Yelk balls are found abundantly mixed with the young 

 in these tubes. 



5. — A, an early stage of young, showing it enclosed in a membranous sac. 

 B. — The larval form as it appears when discharged from the parent. 



Mytilus edulis. 



■\ — A, a transverse section of the generative gland, containing immature 

 spermatozoa. B, — A highly magnified perfect spermatozoon. The point of this 

 spermatozoon moves at right aDgles to its length, C, and presents a very curious 

 and interesting appearance when in active movement. 



2. — A, a more advanced stage, when spermatozoa are present, which are 

 shown expressed at B ; the section is through the long diameter of a lobule. 



3. — A, a lobule with eggs. B,— Eggs. The micropyle is shown. 



4 # A, a branched portion of ovarian tubing. B. — A yelk ball. Yelk bulls 



are abundantly distributed among the young in the tubes. 



5. — A, an early form of young. 



B, the larval form as discharged from the parent. 



Ostrea edulis. 



1. — A, a drawing of a stained section of generative gland, containing 

 immature sperm bundles. The darker portion shows distribution of the male 

 element ; the line above represents the surface of the animal. B, a perfect 

 spermatozoon highly magnified. 



2. — A, the sperm bundles mature and breaking up, drawn from a stained 

 section of gland, out of which the clear cells and bundles of spermatozoa at C 

 were expressed. D, shows a perfect bundle of spermatozoa, with their extended 



