PELAGIC PLANT LIFE 355 



of oceanic species, that we subsequently met with in the central 

 parts of the ocean, though there was not more than a mere 

 selection of the very commonest forms. It was here that we 

 first became aware of the immense contrast between the scanty 

 plant life and the teeming animal life. Sir John Murray and I 

 examined the stomach contents of the salpee abounding in the 

 Strait of Gibraltar, and could see that they lived almost entirely 

 on small forms like coccolithophoridse and tiny peridinese, 

 which were too diminutive for our silk nets to capture. 

 Radiolaria, however, both Acanthometridae and colony-forming 

 species, in symbiosis with brown flagellates, were present 

 sometimes in such quantities that their assimilation of carbonic 

 acid played no small part in proportion to that of the scanty 

 plant plankton. Close in to the shore, on the other hand, there 

 was abundance of plankton, and we got quantities of neritic 

 diatoms off Lisbon, in the Strait of Gibraltar, and at several 

 places on the coast of Morocco down to Cape Bojador. Different 

 species predominated in the different samples, but Laiideria 

 aimulata was the commonest form everywhere. 



No one accustomed to the plankton algae of northern waters, 

 with their numerous dark-brown chromatophores, could fail 

 to be struck by the fact that the species never had more 

 than a few small chromatophores, and thus had a pale 

 appearance. In the diatoms the strong light frequently had 

 the effect of making the chromatophores group themselves in 

 the centre of the cell, or in Lmtderia annulata at the terminal 

 faces where the cells in the chain touch each other. This was 

 invariably the case in plankton near the surface, though deeper 

 down the position of the chromatophores might be normal.^ 



On this cruise we made acquaintance with the tropical The Central 

 Atlantic plankton in all its abundance. For a northerner it ;A^tia'itic from 



V • • -11 r ' • 11 "^"^ Canaries 



was most tascmatmg to study the many strange forms, especially to the Azores, 

 of peridineae. Every fresh batch disclosed species that were A^oresTo^he 

 new or rare, or else remarkable stages of development. The Newfoundland 



1 The following list is from a sample pumped up from the surface, off the south coast of gg 28th May 

 Portugal, on 24th April 1910 :— 29th Tune.)' 



Diatoms : Lauderia anmilata (the prevailing form, found with auxospores), Thalassiosira 

 subtilis, T. gravida, Stephanopyxis turris, Paralia sulcata, Coscinodiscus concinnus, Lepto- 

 cylindrus danicus, Rhizosolenia alata, R. shrubsolei, R. styliformis, R. stolterfothii, 

 R. delicatula, R. robusta, Chatoceras densum, C. schiittii, C. didymu))i,C. curvisetum, C. decipiens, 

 C.'lorenzianum, C. diversum, Eucanipia zodiacus, Hemiaulus hauckii, Biddtdphia mobiliensis, 

 Bacteriastrujn varians, Nitzschia seriata. 



Peridineee : Ceratium lineatttm, C. macroceros, C. fusus, C. furca, C. candelabrum, species 

 of Peridinium, Gonyaulax spinifera, Diplopsalis leiiticula, Dinophysis acuminata, D. rotundata, 

 D. acuta; Coccolithophora pelagica. 



