being the only known Fucoid which is truly a parasite. The 

 Nufhcia grows constantly upon the spore-cavity of the Ilormosira, 

 and its fronds, however different in aspect, have just so much 

 afHnity in development with those of Uormosira that one is 

 tempted to guess at the possibility, at least, of this parasite being 

 an abnormal proliferous growth from the hymenium of the nobler 

 species. Were the occurrence of the Notheia rare, such a view 

 would be strengthened ; but it is far too common along a great 

 extent of coast, and far too regular in its development, to favour 

 such an opinion, in the absence of direct evidence of its truth. 

 There is also, in the development of the frond, a greater affinity 

 with Sj)lachnidium than with Uormosira. 



The spores, in the specimens examined, are scarcely fully 

 organized, and no antheridia have been observed. 



This parasite was first collected by the naturalist attached to 

 Captain Wilkes's Exploring Expedition. 



Fig, 1. Notheia anomala, — the natural she. 2. Part of a branch, with ra- 

 muli. 3. Cross section of a ram\ilus ihwugh. ihvee sca^hidia. 4. One of 

 the scaphidia or spore-cavities : — magulfied. 



