ASYMMETRY IN THE STARFISH. 125 



First Census (5 days old). 



Control 87 % of larvae have left posterior ccelom 



13% ' right 



i, A (iced i hr.) 56% left 



44% " " " right 



i, B (iced 2 hrs.) 79%" " " left 



21% " " " right 



i, C (iced 3 hrs.) 36% ' left 



14% " " " right 



50% median " 



Note: In the last lot it was impossible to decide in just half of the larvae whether 

 the posterior ccelom was destined to go to the left or to the right. The culture was 

 somewhat belated and at this time and the asymmetry matter was unsettled in many 

 of the larvae. Yet those that have settled their asymmetry show 72 per cent, with 

 left-hand asymmetry as compared with 28 per cent, with right-handed asymmetry, 

 a result very closely consistent with that shown in the second census of the same 

 lot. 



Second Census (six days old). 



Control 97% of larvae have left water pore and pore canal 



3% right " 



i, A (iced i hr.) 71 %" " " left 



29% ' right " 



i, B (iced 2 hrs.) 74%" " " left 



26% " " " right " 

 i, C (iced 3 hrs.) 72%" " " left 



13% " " " right " 



15% ' both right and left water pores 



and pore canals 



Third Census (ten days old). 



Control 98 % of larvae with left asymmetry 



2% " " " right 



i, A (iced i hr.) 89%" " " left 



11% right 



i, B (iced 2 hrs.) 88%" " " left 



12 % " " " right 



i, C (iced 3 hrs.) 6i%" " " left 



21% right 



18% " " " bilateral symmetry 



Note i. At this time it was evident that the experimental larvae, especially 

 those in Lot i, C, were smaller and less advanced than the control. It was necessary 

 to discard from those chosen for the census all distinctly abnormal larvae and those 

 in which no water pores or pore canals had developed, and there were many of these. 

 The suppression of these structures in experimental lots is in itself an important 

 result, and is considered simply a more marked expression of the same morpho- 

 logical response that is shown in disturbances of symmetry. 



Note 2. In connection with the 18 per cent, of bilateral larvae listed for Lot i, 

 C in the last census, it should be noted that the paired water pores and pore canals 

 were rarely equal in size, sometimes that of the left side and sometimes that of the 

 right side being larger. 



