518 ABSTRACTS~~OF MEMOIRS. 



Report on the Distribution of the Microplankton. By L. R. 



Crawshay. {Report on the work carried otif hij the ss. ^^ Scoft'a,'' 1913. 

 (Pages 68-126, Ptates 23-35.) H.M. Staiionerij Office, London. 1914.) 



The purpose of the Scotia Expedition to the North Atlantic in 1913 

 having been to study the movement and distribution of the ice in the 

 region of the Labrador Current, the subject of the Report on the plank- 

 ton investigations concerns the distribution of the microplankton, 

 especially the Diatoms, as regulated by the Labrador Current on the 

 one hand, and by the warm Atlantic water on the other. 



The area of investigation extended roughly between 44° and 55° N., 

 and between about 44° W. and the coastal water to the westward. 



The species dealt with are very largely neritic forms, characteristic of 

 the polar water, and the distribution of these as contrasted with that 

 of certain oceanic species, especially Rhizosolenia stylijormis, was found 

 to conform very closely with the distribution of the Labrador water as 

 ascertained by the hydrographic observations. Among the species 

 considered, a third class is distinguished as " intermediate " species, as 

 including those which possess a wider hydrographic range, and of which 

 the hydrographic relations are of chief importance in their bearing on 

 secondary details. Such importance have the distribution of the Peri- 

 dinidse in the month of July, after the decline of the neritic Diatoms, and 

 the distribution of Ceratium arcticum as compared with that of C. 

 long i pes. 



The report is divided into two sections, dealing with the surface and 

 vertical distribution respectively of the species considered. 



The first section is illustrated by a series of charts showing the dis- 

 tribution, as observed over four periods between April and July, of 

 certain of the more important species. These four periods correspond 

 with those observed by Mr. Matthews in the construction of his charts 

 of the physical conditions, with which the plankton charts may there- 

 fore be directly compared. 



Up till the end of June, the seaward boundary of the neritic species 

 was found to follow, north of the Grand Banks, approximately the 

 34-50 isohaline and an isotherm somewhat above 4°. Outside the 34-70 

 isohaline and the 5° isotherm they were only recorded in a single instance, 

 in an isolated patch of 34-50 water, and the whole of this region was 

 tenanted by an abundance of Rhizosolenia stylijormis, in company with 



