818 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



If the numbers of Neritic occurrences be added up 

 for each mouth, they show that mid-winter (December and 

 January) and mid-summer (July) are more Oceanic in 

 character than the intervening months, April, May and 

 October being the most Neritic. 



" Monotonic " Plankton. 



Although many naturalists in the past have recorded 

 the occurrence of dense crowds, " banks " or " swarms " 

 of some one surface animal, or the members of one group, 

 not merely round coasts but even in the open sea, Haeckel 

 was the first, in 1890, to draw attention prominently to 

 this important point in the distribution of the plankton, 

 and to give it a distinctive name. In " Planktou-Studien," 

 p. 57, he says: — "Die Zusammensetzung des Plankton 

 aus verschiedenen Organismen ist sowohl in qualitative!' 

 als in quantitativer Beziehung sehr ungleichmassig, und 

 ebenso ist die Yertheilung desselben im Ocean nach Ort 

 und Zeit sehr ungleich ; diese beiden Grundsatze gelten 

 ebenso fur das oceanische wie fur das neritische 

 Plankton." And further on, at p. 60, he distinguishes 

 between " polymiktes " and " monotones " plankton, and 

 says of the latter that this monotonic plankton shows a 

 very liomogeneous composition; and when a single pre- 

 vailing species, genus or family forms more than three- 

 fourths of the whole mass of the plankton, he regards it 

 as a case of " uniform monotonic plankton." 



Monotonic planktons are found frequently around the 



British Islands, and we have described some examples 



from the Irish Sea in the past. We desire to place on 



record a few additional cases, and to illustrate some of 



them by photo-micrographs* kindly prepared for us by 



our friend Mr. Edwin Thompson of Liverpool. 



* These were originally made by Mr. Thompson in the Spring of 1900. 

 and were shown as lantern illustrations to Professor Herdman's Evening 

 Discourse before- the British Association at Winnipeg in August. They 

 have since been shown at the Royal Institution lectures (London), on 

 "The Cultivation of the Sea," in January, 1910. 



