230 DONALD WALTON DAVIS 



an indication that among individuals with higher numbers of 

 stripes a preponderance of specimens have completely re- 

 generated; while among the lower numbers a great proportion 

 have recently divided and regeneration of stripes has not begun 

 or has at least not been completed. Such counts as have been 

 made further indicate with some degree of probability that 

 divisions are more frequent in the spring and less frequent 

 toward fall (p. 222ff.). 



By the processes of regeneration described, a rather definitely 

 fixed set of structures is added to a piece resulting from division, 

 regardless of the form of that piece (pp. 185 to 192). The outer- 

 most mesenteries of this set are modified to match up with the 

 old bounding mesenteries. Since the forms of old pieces are 

 quite various (p. 181), the resulting individuals are likewise 

 diverse in the number of siphonoglyphs, mesenteries and orange 

 stripes (pp. 184, 192). With rarest exceptions the variations 

 from the typical Hexactinian form may be accounted for on the 

 basis of the processes of asexual reproduction described. Re- 

 peated fission and regeneration tends to produce specimens with 

 approximately eight pairs of complete mesenteries and sixteen 

 orange stripes (pp. 198, 215). The fact that actual counts of 

 mesenteries in specimens of the groups studied show a distinctly 

 lower average than this, indicates that the sexually derived form 

 possesses fewer than eight pairs of complete mesenteries. 



The fundamental form of the species, i.e., that resulting from 

 ontogenetic development, has not been ascertained. It is prob- 

 ably biradially symmetrical and hexameric, with two siphono- 

 glyphs (pp. 218 to 220) and six pairs of complete mesenteries 

 (pp. 220, 221), two pairs of which are directives. 



Sexually mature individuals of both sexes have been found, 

 but the development of the fertilized egg has not been followed. 

 The failure to obtain developmental stages, together with the 

 abundance of stages in asexual reproduction (p. 220fT.), suggests 

 the probability that the latter constitutes the chief means of 

 maintaining or rapidly increasing the population of a given 

 region. 



College of William and Mary, August, 1917. 



