86 



occupies a longer time in the course of development tlian 

 any other. Under laboratory conditions, the 3-celled stage 

 is retained at least several days, and frequently develox^- 

 ment goes no further. The factor determining furtlier de- 

 velopment seems to "be, in v-d^rt at les.st, the cha,racter of 

 the suhstratum. In the cultujr-es exairdned, it -..as found 4ii 

 that on glass or on clean, though rough stones, the basal 

 cell continued to elongate, though without further division 

 of the apical cell, until the whole sporeling lost its nat- 

 ural color and died. However, i^ji case the elongating basal 

 cell came in contact v/ith some soft substance, it fastened 

 itself iimnediately , and norme.l development proceeded. In 

 a state of nature, young sporelings of G riff ithsia have 

 been most coi-oinonly found at V/ood's Hole, on Champ ia pa.rvula 

 and on Lomentaria uncinata , t hough they occur on other al- 

 gae and on Zostera marina . Young plants were sometimes 

 foxmd on stones, the surface of v/hich a^ppeared clean, but 

 proved., on cai^'eful examination, to bear other sporelings, 

 to which the plantlets of Griff ithsia were probably e.t 

 first attached. There is no evidence of parasitism, how- 

 ever, in the early development of Griff ithsia . Sporelings 

 floiirish on any soft substratum, such as bits of cotton 

 cloth. From tlie observations noted above, it seems clear 



