THE NATURAL HISTORY OF THE SEA. 393 



in search of work. P>om the researches of Dr. Schiltt and 

 several distinguished predecessors, it appears that we must 

 regard the Peridiniecp (and some alHed minor groups) as 

 related to the diatoms from the structure of their membranes, 

 mode of division, chromatophores, etc. Their membranes 

 are not silicified like those of the diatoms, their valves 

 frequently consist of several plates, their girdles are of 

 different structure, they possess propelling whip-lashes, but 

 in all or most of the points of difference the parts in 

 question are comparable each with each, though the homo- 

 logies, as Dr. SchLitt states them, may appear sometimes a 

 little strained. The new shells or valves of the PeridimecE 

 not being produced within, or overlapped by, the older 

 membranes, they do not steadily diminish like the diatoms, 

 and their life history is therefore not complicated by the 

 production of auxospores. Moreover they appear to play 

 the same part in the economy of the sea, as the diatoms do, 

 in furnishing with them the great bulk of the nutriment for 

 marine animals, the basis of most fishery problems. Dr. 

 Schiitt in the latter of the two works cited deals with some 

 of the allied minor groups, such as Gymnodiniacece, the in- 

 clusion of which may be questioned by some authorities. 

 As for Pyrocystis (the source of tropical luminosity in many 

 cases) be it a state of Koctibica as Moseley, Biitschli and 

 others have contended, or be it a plant as others still hold, 

 its place is at all events not in GymnodiniacecB. This part 

 is in several respects the least satisfactory of Dr. SchLitt's 

 work, and his treatment of the diatoms (Bacillariaceae) will 

 meet with adverse criticisms from the special students of 

 these organisms. However all owe him thanks for the 

 compendious account of the whole series given in Eiigler 

 und Prantl ( 5 ). 



Diatoms have so long been a weariness to every natur- 

 alist, other than the sect of devotees of their study, from 

 the fact that this study has consisted of mere records of 

 markings and the performances of particular high power 

 lenses mixed with unscrupulous jugglings in the nomen- 

 clature of forms, that it is refreshing to come upon 

 discoveries of living interest to cultivated readers of natural 



