518 THEOPHILUS S. PAINTER 



were meridional, that is, cut the pigment band at right angles. 

 In the living egg the spindle did shift until it occupied the posi- 

 tion in which the pigment band would be cut, either in the first 

 or second cleavage plane. That the eggs found in a study of the 

 sections show phases of this shifting process is scarcely to be 

 doubted in the light of all the facts. 



A number of authors have recorded the appearance of spiral 

 asters in the eggs of widely separate groups; Nemerteans, Mol- 

 luscs, Annelids, and in at least one vertebrate, Axolotl (Fick, 

 '93). The phenomenon has been more frequently described for 

 the molluscs, and it seems confined to the gastropods. Mark 

 ('81) was the first to describe and figure spiral asters, in Limax 

 campestris. In this form they appeared, somewhat inconstant- 

 ly, at the time of the second polar body formation. At least four 

 other authors have recorded spiral asters in various snails at 

 this period of the maturation. Kostanecki and Wierzejski ('96) 

 mention it for Physa. MacFarland (^96) observed and has given 

 excellent figures of it in Pleurophyllidia ; Byrnes ('99) decribes 

 it for Limax agrestis; and Linville ('00) notes its occurrence in 

 Limax maximus. 



None of these authors have attempted to explain the cause of 

 the spiral aster. Conklin ('02) and ('05), however, has described 

 in detail the movements taking place in the protoplasm of the 

 eggs of Crepidula, and the Ascidian cynthia during maturcition 

 and cleavage. From the observations of this author it is clear 

 that materials are constantly being shifted from one part of the 

 egg to another in both of these widely separated forms. Kosta- 

 necki and Wierzejski have noted that the same was true of Physa. 

 Conklin points out, in discussing these movements ''that the 

 movements within the cell substance of the unsegmented egg are, 

 in certain cases at least, of a vortical character is indicated by 

 the spiral asters, first described by Mark for Limax, and since 

 observed by several other investigators in other animals, and 

 also by my observation that the first cleavage in Crepidula is a 

 spiral one, being oblique to the right or dexio tropic" (p. 79, 

 Karyokinesis and Cytokinesis). 



