Makch 2, 1917] 



SCIENCE 



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ical and developmental researches. The 

 progress along this line has led to other 

 studies of histological and developmental 

 details. These in turn have led up to the 

 present condition, when it seems desirable 

 to make a new and more detailed study of 

 all species, but especially of those credited 

 with a wide geographical distribution or 

 with great variability. 



The third and latest period of taxonomic 

 development has resulted in a newer view 

 of specific limitation, in other words, has 

 resulted in specific segregation being car- 

 ried to a much greater degree than hitherto, 

 yet seemingly not beyond reasonable lim- 

 its. The results may be seen from Kjell- 

 man's treatment of Galaxaura (1900), 

 Falkenberg's treatment of the Bhodomela- 

 cem (1901), A. and E. Gepp's treatment of 

 the Codiacece (1911), Sauvageau's treat- 

 ment of the Sphacelariacece (1900-1914), 

 Howe's treatment of Halimeda and other 

 genera (1905-1914) as well as of other 

 groups, Poslie's treatment of the crustaee- 

 ous corallines, Boergesen 's treatment of the 

 algae of the Danish "West Indies (1913- 

 1916), my own treatment of Scinaia (1914), 

 and others. In my own study of various 

 genera of the red algae, both from the point 

 of view of morphological differences and of 

 geographical distribution, it is necessary to 

 more carefully distinguish and separate the 

 true species in the case of many aggre- 

 gates and to scrutinize very carefully those 

 species credited with extended or widely 

 discontinuous distribution. The results 

 throw a much clearer light on certain seem- 

 ingly troublesome points of geographical 

 distribution, both climatic and topographi- 

 cal. 



The anatomical and histological aspects 

 of the morphology of the marine algae were 

 earlier treated of in connection with the 

 taxonomy. In the first period of taxonomy, 

 the study of the structure both of the vege- 

 tative and reproductive portions was slight, 



although some progress was made through 

 Reaumur (1711), Stackhouse, Turner and 

 others. In the second taxonomic period, 

 Lamouroux gave a great impetus to the 

 study of structure and the distinctions be- 

 tween the different methods of fructifica- 

 tion and towards the last of this second 

 period the knowledge of structure was 

 placed on a fairly firm basis. 



It was during the third taxonomic period 

 that the study of morphology may really be 

 said to have originated as a separate sub- 

 ject and much of the credit for properly 

 emphasizing it came from Thuret, both by 

 his own publications and by those in con- 

 nection with Bornet. Since then many 

 special papers dealing with the adult or 

 developmental morphology have been pub- 

 lished. Cytological work, too, has been 

 carried on to a considerable extent. The 

 cell membranes have been studied by Cor- 

 rens and others; the chromatophores by 

 Schmitz and his successors; various cell 

 contents, including the plasma massing in 

 the cells of iridescent marine algae by 

 Berthold and others. The study of the 

 nucleus and its division has engaged the 

 attention of many investigators from 

 Schmitz (1879) through Pairchild, Swingle, 

 Farmer, Strasburger, Osterhout, Williams, 

 Wille, B. M. Davis and Oltmanns. Ya- 

 manouchi and Svedelius, in particular, have 

 investigated the chromosome niunber in 

 connection with the alternation of genera- 

 tions of red algae. The morphology, both 

 gross and minute, of holdfasts, vegetative 

 and reproductive organs, have been, and 

 still are being, given most careful attention, 

 in connection with taxonomic, physiolog- 

 ical and ecological investigations. 



Wliile most attention has been turned 

 towards the morphology and development 

 of the marine algte, their special physiol- 

 ogy has received some attention. By far 

 the greater portion, however, remains to 

 be done. It is impossible to more than call 



