OVARY AND OVARIAN OVA IN CERTAIN MARINE EISIIES. 149 



demonstrated by fixing with clirom-acctic acid and staining 

 with hsematoxyliu and orange G. After sucli treatment 

 in the germinal vesicle, when the nucleoli are still at the 

 periphery, there is seen a more deeply stained and more coarsely 

 granular body in the central region. This is the appearance 

 with a low magnification; with higher powers the body is seen 

 to consist of broad winding chromatin cords, composed of 

 threads transverse to their direction, i. e. having the structure 

 which I have called feathery. These feathery threads contract 

 into thinner, denser threads which break up into separate 

 chromosomes : during this process the nucleoli move in a 

 centripetal direction, surround the aggregate of chromatic 

 fibrils, and gradually disappear, some breaking up into pieces, 

 others becoming pale and dissolving. 



In 1893 Rudolf Fick (10) described the corresponding trans- 

 formations in the ovum of the axolotl. He observed that the 

 nucleoli vanished completely, but leaves open the question 

 whether there is any connection between their disappearance 

 and the development of the chromosomes. 



In a still more recent paper (1895) E. Korschelt (17) describes 

 the maturation of the ovum in the chsetopod Ophryotrocha 

 puerilis, and states that the single nucleolus present vanishes 

 by dissolution while the convoluted chromatic thread is 

 developing, but leaves undecided the question whether the 

 substance of the nucleolus is transferred to the thread. 



In one of the Foraminifera the chromatin of the nucleus 

 is in the form of elements which have a curious resemblance 

 to the nucleoli seen in the germinal vesicle of the Teleostean 

 ovum, but in the present state of our knowledge it is impossible 

 to say whether any great importance is to be attached to this 

 resemblance. Fritz Schaudiun (18) has described the history 

 of the nucleus in Calcituba polymorpha, and the following 

 is a summary of it. The protoplasm of the animal is multi- 

 nucleate. The largest nuclei are 10 to 35 fx in diameter, and 

 consist of a vesicle bounded by a membrane. The central part 

 is filled only with structureless nuclear sap, while the chro- 

 matin lies on the inner surface of the membrane in the form 



