484 ' THEOPHILUS S. PAINTER 



'SPINNING' OR 'FILOSE ACTIVITIES' IN THE LIGHT OF MONASTER 



EGGS 



The protoplasmic movement of monaster eggs is similar, 

 in several respects, to the ' spin-thread', or 'filose activities' 

 observed by several investigators (G. F. Andrews '97, E. A. 

 Andrews '98, Coe '99, C. B. Wilson, '99) in the polar body for- 

 mation and in the cleavage of nemertean eggs. Also in star- 

 fish and sea urchin eggs as described by Mrs. Andrews. 



As far as the protoplasmic activity of Cerebratulus is con- 

 cerned, I believe the movements so well described by C. B. 

 Wilson, and which I have myself observed on this same material, 

 may be directly compared to those found in monaster eggs, 

 since: first, they are found in the region of the cleavage furrow; 

 and, second, are found just when cytoplasmic division is taking 

 place, or has just been completed. So far as I am aware, noth- 

 ing comparable to the swelling of the ectoplasmic layer has 

 been described for the nemertean egg. 



The 'filose activities,' described by Mrs. Andrews, were not 

 limited to the division plane, but occurred at any place on the 

 eggs surface and at any time in the division cycle. What rela- 

 tion these general activities bear to the periodic movements, 

 described in this paper, is not altogether clear. The work of 

 Goldschmidt and Popoff suggests a possible explanation. They 

 observed that when eggs were placed in hypertonic sea water, 

 the protoplasm lying just beneath hyaline layers underwent 

 changes in form, during which little threads were formed; these 

 branched and anastomosed, just as Mrs. Andrews described. 

 Under the conditions which Mrs. Andrews' work was made, 

 it seems very likely that an evaporation of sea water took place, 

 with the consequent increase in the density of the sea water. 

 This may have been the primary cause for the activities which 

 Mrs. Andrews observed. In this event, the periodic movements 

 during certain phases of the division cycle, and the continuous 

 activities, would be similar in so far as they are responses of the 

 cytoplasm to the same stimulus, namely, changes in density. 

 In the one case, however, the changes come from within (mon- 

 aster eggs), in the other, from without. 



