DEPARTMENT OF MARINE BIOEOGY. 127 



It is proposed to prepare a systematic study of the annulata of the entire 

 West Indian region, and work has begun on a monograph of the Eunicidse, 

 a group well represented in this region. The paper is to be illustrated with 

 water-color drawings of the living animals, and a number of these were 

 made this season by Mr. Morita. 



Summary of Experiments on the Development of Eggs, by J. F. McClendon. 



Eggs of the gulf-weed nudibranch Scyll(ca pelagica (edzvardsii) mere strat- 

 ified by centrifugal force, but developed normally except for pigmentation. 



In the egg of Spirohranchus tricornis the pigment is dissolved in oil, which 

 is in the form of droplets. These drops were separated out by centrifugal 

 force, and tested with Sudan III before and after separation. The imma- 

 ture egg can be fertilized with sperm if put into 50 c.c. sea-water containing 

 2 drops of M/io NH.OH. 



The immature egg (germinal vesicle intact) of Ophiocoma rizii pushes 

 out a membrane when placed in 50 c.c. sea-water containing 3 c.c. M/io 

 acetic acid. A few matured when left 12 hours in 50 c.c. sea-water contain- 

 ing I drop of M/io NH4OH. 



The eggs of Echinastcr crassispina are very large in comparison to those 

 of other echinoderms. During the growth period their specific gravity de- 

 creases. The small eggs are heavier than sea-water and the full-grown 

 eggs lighter than sea-water. This change is due to the accumulation of oil 

 in drops throughout the cytoplasm. The oil was separated by centrifugal 

 force and tested with Sudan III before and after separation. Brown pig- 

 ment granules are distributed throughout the cytoplasm, but may be sepa- 

 rated out (precipitated) by centrifugal force. The large germinal vesicle 

 lying adjacent to the surface of the egg is so transparent that there appears 

 to be merely a depression in the opaque cytoplasm where it lies. An elec- 

 tric current was passed through eggs that had been sucked up into capillary 

 tubes and placed under the microscope. Each egg became paler toward the 

 anode and darker toward the cathode. Owing to the opacity of the cyto- 

 plasm, the movement o£ individual granules could not be followed, and it 

 could not be determined whether the pigment was moved by electrical con- 

 vection directly, or indirectly by the current. With too strong a current the 

 pigment is destroyed. All attempts to ripen the eggs failed. 



The unfertilized eggs of Toxopneustes (Lytechinus) variegatus and Trip- 

 nenstes (Hipponoe) escitlentns were made to segment by treatment with 

 sea-water containing ammonia, acetic or carbonic acid, or excess of NaCI 

 (hypertonic). In Toxopneustes a membrane (composed of or covered by 

 granules) was pushed out after treatment with carbonic acid, but not in 

 Tripneustes. An attempt was made to find the best method by which to 

 produce artificial parthenogenesis in these eggs, and no better could be 

 found than Loeb's method of treatment with acid followed by hypertonic 

 sea-water. The eggs of the two species and of different individuals re- 

 quired different durations of the treatment. By increasing the duration of 

 the treatment the rate of development was increased (approached that of 

 fertilized eggs), but the percentage of larvae developed decreased, indicating 

 injury to the eggs. For Toxopneustes 1.5 to 5 minutes in sea-water car- 

 bonated in a Sparklet siphon and 30 to 45 minutes in 100 c.c. sea-water plus 

 16 c.c 2.5 M NaCl was best. If the eggs have remained long standing, a 

 shorter stay in carbonated sea-water is required than if they are fresh, indi- 



