502 MARGARET MORRIS 



own species. The pipettes were not only carefully washed, but 

 were marked besides, so that the one used for Fundulus sperm 

 was never used for unfertilized or hybrid Fundulus eggs. Dishes 

 were carefully washed and dried, and a control lot of unfertil- 

 ized eggs from the same lot as the hybrids was always kept. No 

 eggs were found in any of these control lots that had divided. 



The eggs of Fundulus have a diameter of about 2 mm., while 

 those of Ctenolabrus are about 1 nun. in diameter. Both kinds 

 were handled as follows: they were expressed into a finger-bowl 

 containing a small amount of water. A mmiber were taken out 

 for two controls, one of which was normally fertilized and the 

 other left unfertilized. The rest of the eggs were fertilized with 

 the foreign sperm, and more water was added to all three lots 

 to keep them fresh. 



The eggs were preserved in series at varying intervals, the 

 fluids used being Gilson's, Bouin's, and Perenyi's for the Fundu- 

 lus eggs and Flemming's strong mixture and Perenyi's fluid for 

 the Ctenolabrus eggs. The method of embedding and section- 

 ing used by Moenkhaus on Fundulus eggs worked very well for 

 those preserved in Bouin's fluid. After the tough outer mem- 

 brane had been removed, the eggs were embedded with the blasto- 

 disc ui:)permost, and sections 8 to 10 /x in thickness were cut hor- 

 izontally through the blastodisc. The eggs preserved in Gilson's 

 and Perenyi's fluids were differently treated, as a touch of the 

 needle removes the blastodisc from the yolk, and it is best to 

 embed the former alone. The Ctenolabrus eggs are more trouble- 

 some. They are too small to be easily embedded in a definite 

 position, so the sections must be cut at random. Moreover, those 

 preserved in Flemming's mixture are so dark that it is necessary 

 to bleach them. I used Mayer's method, bleaching the sections 

 on the slide, but found that sections so treated did not take the 

 stain well. The stains used were Heidenhain's hematoxylin and 

 iron alum, and Ehrlich's hematoxylin counterstained with Congo 

 red. The latter is more satisfactory, as there are granules in 

 the cytoplasm of the Fundulus egg which are stained by the 

 iron hematoxylin method and may be confused with small chro- 



