ON EGGS OF MARINE ANIMALS 27 



I have taken but one specimen. The ovaries of a large ripe 

 female will fill a dish of 200 cc. capacity. 



Asterias shed eggs readily in the laboratory. In June, 1927, 

 for example, I had a great deal of difficulty because of this fact. 

 The first normally shedding male and female I ever used were 

 kindly turned over to me in 1910 by Dr. John W. Scott. Since 

 then I have recorded many observations on animals shedding 

 in the laboratory. Every one of these was during full moon, 

 never during new moon. The average worker would hardly care 

 to await the chance of procuring normally shed eggs. This is 

 indeed not necessary, since he can obtain eggs of optimum 

 viability by removing the ovaries to sea-water. 



In the interest of economy it is well to make a slight puncture 

 in an arm close to the disc, and pipette oilF a few drops of cells 

 from the gonads. The animal is not seriously injured thereby 

 and its sex may thus be ascertained. The animals are best 

 opened as follows: 



Make a cut along the mid-dorsal line of each arm beginning 

 at the tip and across the central disc. Bend back the flaps thus 

 made and expose the gonads. If the animal be a ripe female 

 with well filled ovaries, with forceps carefully remove each 

 ovary with as little injury as possible and place it in at least 

 2000 cc. of sea-water in a large flat-bottom dish. Do not cut up 

 the ovaries; the eggs will exude freely. When the eggs from the 

 blunt end of the ovary have streamed out into the sea-water, 

 remove the ovary, for you now have the best eggs. Stir the 

 water gently and then allow the eggs to settle. (They settle 

 more slowly than those of Arhacia.) After the eggs have settled 

 pour off the sea-water and add an equal volume of sea-water. 

 Note under the microscope the break-down of the germinal 

 vesicle. If the eggs are in good condition practically not a single 

 one will show an intact germinal vesicle. 



If the animal opened proves to be a male, cut through oyie arm 

 only. Snip off a small bit from the blunt end of the testis and 

 place this in 200 cc. of sea-water. The sperm, contrary to the 

 somewhat current notion, are highly active, although not as 

 much so in concentrated suspensions as those of Arhacia. 



I venture the opinion that workers experience difficulty in 

 handling eggs of Asterias, even when they have animals in perfect 



