422 TRANSACTIONS OF SECTION D. 



It is quite impossible for such large quantities to be caught and equally 

 strange that remains of the creatures are so rarely found if they have been 

 captured as food. Putter has given figures for Anthozoa, Rotifera, Crustacea, 

 Tunicata, and even fishes. 



The figures for the entomostraca are particularly interesting, because the 

 copepoda are supposed to play such an important part in the economics of the 

 sea. For a long time the actual solid food of the copepoda was unknown. The 

 writer was able, after the examination of a large number of individuals, to show 

 that one could find remains of diatoms, Peridinium, and very small naked 

 flagellates which passed through the finest silk. Putter's calculations demand, 

 however, for a Calanus, 9,750,000 Thalassiosira nana per day ! He asks if it is 

 possible for such a quantity of food to be captured by a copepod. 



It has been found that gold-fish living in tap-water without solid food can 

 exist for forty-one days, and during this period the amount of oxygen consumed 

 is equivalent to that required if calculations are made from the loss of weight 

 of the fish. If, now, organic substances in solution are added to the water, the 

 same species live seventy-eight days, and the oxygen consumed per fish is in 

 excess of the amount calculated from the loss in weight — i.e., the oxygen must 

 have been used for the oxidation of substances in addition to those stored in 

 the tissues. 



We may divide the plankton organisms into two contingents, that of the pro- 

 ducers and that of the consumers. To the first category belong the organisms of 

 the phytoplankton which make use of dissolved inorganic substances, and to the 

 second the animals. Now calculations have shown that the ' producers ' are 

 insufficient for the 'consumers.' This is a very powerful argument in favour of 

 Putter's theory, and even the Kiel planktologists (who have been in general 

 against Putter from the first) have had to seek for another source of food for 

 the zooplankton (Lohmann's detritus theory). 



One finds that the copepoda are usually most abundant after the maxima of 

 the phytoplankton. This has been accounted for by some workers by assuming 

 that the increasing copepoda destroy the phytoplankton. May it not be that the 

 increase of the copepoda is due to the large quantities of available dissolved 

 organic matter due to the death and disintegration as well as to the destructive 

 metabolism of the plants of the antecedent phytoplankton maximum ? Only a 

 few weeks ago attention was drawn to the fact that in the high Alpine lakes 

 there exists an outstanding production of zooplanktonic organisms. What is 

 the source of food of these Alpine Crustacea and Rotifera ? The lakes are almost 

 deserts as far as phytoplankton is concerned. Putter's theory is the only 

 solution of the riddle. 



Finally there must be taken into account the great difficulty, so often 

 experienced, of finding the remains of organised food in the alimentary canals 

 of many aquatic organisms. We have, too, crabs living in sponges, and with 

 only filtered water at their disposal, and Knorrich and Wolff have been able 

 to keep Daphnids living and growing in solutions containing only dissolved food- 

 matter. 



There are many other points which may be cited in favour of the theory, and 

 much which may be brought forward against it. The latter I have left for pur- 

 poses of discussion. I myself believe that, though solid food is necessary, yet 

 food in solution also forms part of the normal food-supply. 



5. On the Systematic Position of the Marsipobranchii. 

 By W. N. F. Woodland. 



A short summary of the arguments demonstrating that the Marsipobranchs 

 are primitively agnathostomatous animals will alone be provided here. The 

 result of recent research on the innervation, musculature, and development of 

 the Marsipobranch head has been entirely to demolish theories which regard the 

 subocular arch and ' lingual ' cartilages (' piston ' cartilages — Bujor) of Marsipo- 

 branchs as respectively homologous with the p.p.q. bar and glosso-hyal element 

 of Gnathostomes. That the subocular arch is not a true p.p.q. bar is alone 

 proved by the well-known facts that the maxillo-mandibular nerves pass ven- 



