THE GENEEATIVE ORGANS OF THE OYSTEB. 281 



DESCEIPTION OF PLATES XXII, XXIII, 



Illustrating the abstract of Dr. HoeVs paper on " The Generative 

 Organs of the Oyster/' 



All the figures after Dr. P. P. C, Hoek. 



Fig-. 1. — View of a freshly opened oyster lying in the left valve after removal of the 

 right valve. A portion of the mantle has been removed to show the oral process situated 

 in the suprabranchlal chamber. 



Fig. 2. — Diagram of an oyster of which a part of the branchia3 and mantle have been 

 removed to show the general arrangement of the generative organs aiad organ of Bojanus. 

 The black lines represent the canals and ducts of the generative organ; the organ of 

 Bojanus is shown in shading. To avoid encumbrance of the figure the genital ducts and 

 canals are made to appear much smaller than they are in reality. U. A. Urogenital aper- 

 ture. Ep. C. llenopericardial canal. 



Fig. 3. — Section of a follicle of the generative organ of an oyster which has laid ova. 

 s'. Mother cells of spermatozoa in division with numerous nuclei, s". Ripe spermatozoa 

 (xl90). 



Fig. 4. — A portion of the preceding figure more highly magnified ( x 900). a. Epithe- 

 lium, h. First stage of division of mother-cell. B. Numerous nuclei derived from the 

 primitive nucleus. A. Stage previous to the separation of the swollen multinuclear mass 

 from its pedicle, y.y. Blood-corpuscles. 



Fig. 5. — Mass of ripe spermatozoa ( x 575). 



Fig. 6.— Ovules on the wall of a follicle, e. Epithelium of the follicle ( x 190). 



