I5O S. J. HUNTER. 



78. Very few whole eggs, nearly all in fragments of halves 

 and less sizes. 



80. Blastomeres remaining together, few fragments. 



82. Three active well-formed blastulae (examination made 

 ten hours after removal from concentrated sea-water). 



8298. The eight cultures taken out during this time showed 

 about the same percentage of development as 82. 

 IOO. No segmentation in this culture nor in any of the sub- 

 sequent cultures. 



This experiment shows a duration of sixteen minutes within 

 which eggs were removed and larval development ensued. This 

 was the widest range of the series. In many experiments a dif- 

 ference of five minutes on either side of the optimum moment 

 determined the life of the culture. In all cases, as noted by other 

 observers, eggs removed from the concentrated solution after a 

 brief period begin to segment but do not continue to develop 

 until they reach the swimming blastula stage. Eggs permitted 

 to remain too long plasmolyze when placed in sterilized sea-water. 

 As a result of this series of experiments the optimum period was 

 determined at two hours. In each case three cultures were formed 

 of the eggs, one of five minutes before the period, one at the period, 

 and the other five minutes after the two hours. 



Temperature. The most favorable temperature obviously is 

 the normal temperature of sea-water. Sudden changes caused 

 by the use of water of a different temperature for replenishing 

 cultures is detrimental. Greeley 1 has shown that blastulse can 

 be developed parthenogenetically in concentrated sea-water at 

 a temperature of 2, 1 1 and at the room temperature of 23. I 

 am convinced that uniform results cannot be obtained from cul- 

 tures kept on the laboratory table. The changes in temperature 

 which occur between day and night materially affect the behavior 

 of the eggs. For this reason towards the close of the season 

 the bowls containing the solutions were surrounded by running 

 sea-water. This insures constancy of temperature as well as 

 approximates the normal temperature. 



'A. W. Greeley, BIOL. BULLETIN, IV., No. 3, p. 132. 



