80 GENERAL DIRECTIONS. 



Possibly the best success in this line has been with the 

 Echinoderms. Echinarachnius is a good genus from which 

 to obtain a series of larvae by artificial fertilization. The 

 sexes are distinct, male and female sexual glands being 

 found in different individuals. While it is not always 

 possible to determine the sex by external coloration, an 

 examination of the interior just under the middle of the 

 upper side will easily betray it. To artificially fertilize 

 Echinarachnius the observer may first make a ring-shaped 

 incision through the aboral calcareous wall allowing the 

 animal meanwhile to remain in the water. Carefully re- 

 move the incised portion, and suck up in a pipette a few 

 fragments of the dark red organs which lie just about the 

 apex. Place these in a watch crystal filled with pure water, 

 and if the fragments thus transferred contain ova they 

 will soon give up little transparent globules dotted with 

 bright red spots. The ovaries are dark red, and the sper- 

 maries white or yellow. 



When a larger quantity of ova is desired, place the fe- 

 male Echinarachnius in a small dish, glass preferred, and 

 with gentle streams of water from the pipette wash out 

 the small globular eggs with care, and then remove the 

 Echinarachnius and larger fragments of the ovary which 

 may have been ruptured from the gland. Then suck up a 

 small quantity of the white fluid from the male Echina- 

 rachnius into the pipette and place it in the watch crystal or 

 dish with the ova. Stir the mixture gently and set aside 

 for an hour and a half at which time, if the process has 

 been a success, the ova will begin to segment. The young 

 plutei can be easily reared from these eggs in great quan- 

 tities, but care must be taken to change the water at least 

 every two days. It is also well to pick out any fragments 

 of sexual glands which may befoul the liquid. ' 



A limited number of Amphiura young may be collected 

 in August and September, possibly in other months, in the 



