ASEXUAL REPRODUCTION IN SAGARTIA 225 



divisions and regenerations in this species tend toward a condition 

 with an average of approximately eight pairs of complete mesen- 

 teries and sixteen orange stripes, the actual averages in the 

 populations studied are less than eight and sixteen. This is 

 presumptive evidence that the form resulting from ontogenetic 

 development possesses fewer than eight pairs of complete mesen- 

 teries and fewer than sixteen orange stripes. It appears from 

 the statements of Davenport ('03, p. 143 and fig. 1) that twelve 

 is a common number of pairs of complete mesenteries. This is 

 clearly an error. Among several hundred sectioned specimens 

 I have found but two with twelve pairs. These are both tri- 

 glyphic individuals and both show clear evidence of having 

 divided. I have not seen a single biradially symmetrical speci- 

 men with twelve pairs of complete mesenteries. Such a speci- 

 men would normally have twenty-four orange stripes, whereas 

 the highest number recorded by Davenport or myself is twenty- 

 two. It seems likely that Davenport mistook incomplete 

 mesenteries of the first order for complete ones. This is the 

 more probable since she indicates that the specimens described 

 as having twelve pairs of complete mesenteries have twelve 

 orange stripes, the number which I have shown to be character- 

 istic of a form with but six pairs of complete mesenteries. Con- 

 sidering all the evidence at hand, it is probable that the sexually 

 produced form is a diglyphic one with six pairs of complete 

 mesenteries, six pairs of incomplete mesenteries of the first 

 order alternating with these, and twelve orange stripes occupy- 

 ing these two sets of endocoels. Specimens of this form may 

 also be produced by regeneration following fission, and all normal 

 departures from this typical form are due to asexual reproductive 

 processes. 



SUMMARY 



Sagartia luciae is typically Hexactinian in form and structure 

 except for the wide variation in number of siphonoglyphs and 

 of pairs of mesenteries. The number of siphonoglyphs and of 

 associated pairs of directive mesenteries varies from one to five. 

 The number of pairs of complete mesenteries including the 



