184 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Pelagic Plankton, always according to Hseckel, may be 

 divided up into three groups, (1) " Autopelagic," those 

 forms which are only found on the surface, (2) " Bathy- 

 pelagic," those which occur on the surface and also at 

 greater depths, and (3) " Spanipelagic," those forms which 

 normally live at considerable depths (i.e., are then zonary 

 or bathybic forms), but periodically come to the surface for 

 a short time — it may be only for a week or even for a single 

 day in the year. The Bathypelagic includes the great 

 mass of Plankton, and it may be distinguished into " Nycti- 

 pelagic," only coming to the surface during the night, 

 " Chimopelagic," only found on the surface during winter, 

 and " Allopelagic," which seem to make irregular vertical 

 migrations, being sometimes on the surface and sometimes 

 in the depths independently of temperature changes. 



Then again, from another point of view, the terms 

 " Holoplanktonic " and " Meroplanktonic " may be use- 

 fully applied, the former to those organisms which can be 

 ranged under Plankton during the whole of their existence, 

 and the latter to such forms as belong, in some stages of 

 their life history, not to Plankton at all, but to the Benthos 

 (either littoral or abyssal). 



Finally, the Plankton wherever it occurs may be 

 " Monotonic " when it is formed almost entirely of one 

 particular organism or group of organisms, or "Polymiktic" 

 when, as is usually the case, a gathering contains a mix- 

 ture or assemblage of a number of different kinds of plants 

 and animals.] 



The dredged and shore material (" Littoral Benthos" of 

 Hseckel) was collected as follows : — 



(A) In Killybegs Harbour, August 10th : 3 hauls of the 



dredge in the forenoon, depth 5 — 10 fms. ; and 

 3 in the afternoon, depth 10 — 15 fms. 



(B) Killary Bay, August 11th, trawled in 20 fms. ; and 



