0(3kiiicsis ill C'crcbratuliis Liictcnis. 393 



('•j;3, pp. 14, 15). Tins seems to show that the sperm causes the con- 

 traction of the egg.^^ 



The action of the centriole upon the ])oloeyte formation, on the 

 other hand, should not he overlooked. The center seems to cause a 

 sudden decrease of surface tension at the spot where the polocyte is 

 to he formed, provided the cytoplasm he in the right state. 



Tn the non-fertilized < gg of Ccvchmiiiliis laclcus treated with a 

 solution of magnesium chlorid a pointed protuberance resembling 

 somewhat the entrance cone of the sea-urchin oiX'J: is sometimes formed 

 at the animal ])ole. This unsuccessful attem])t of polocvte formation 

 may be due to untimely sinking of the maturation figure toward the 

 center of the egg.^^ 



The number and size of the polocytes may vary according to the 

 physiological state of the egg. In some of the unfertilized eggs 

 treated with a mixture of ])otassium chlorid and calcium chlorid 

 (Professor Wilson's material) the ])(»locytes have been produced.^''' 

 The number and size of the polocytes tlius produced showed great 

 variation. Fig. 70 (PI. \X ) is an egg with a ]iolocvte about five 

 hundred times as large as the normal one. Fig. 71 and 72 (PI. IV) 

 are those with four and five polocytes res])ectively (Kostanecki de- 

 scribes the third ])ol()cyte, '02, p. 284). 



VII. Summary. 



A. Observations on the normal egg of C'erebratidiis ladeus: 

 (1) Before the dissolution of the germinal vesicle the yolk 

 granules are arranged radially. 



='riert\vig adds to this oxpfriuicnt auotlHT i»nssiliilit.v wliicli is worth con- 

 sideriug, /. c. this result may he diu' to the LTadunl cliaiij.'c in thi' iintnre of the 

 o("iphisni. since there is a considerahJe interval between I he time ot injury and 

 fertilization. 



■■-The solution used is 20 S M M,!,'('l. and sea water in e(iual parls; this is 

 twice as strong as thai used effectively for causing artificial ]>arthenogeiiesis in 

 the sea-urchin egg. The latter solution has no noticealile effect on the egg of 

 CrrrhnifiilKx. 



'■•■The egg was put in a sohition of 2U/S M CaCl., (210 cc.) -f 20/8 M KCl 

 (100 cc. ) -f Aq m (SOO cc.) and gradually transferred into sea water. They 

 were fi.xed after three liours. 



