DISCOVERY 



265 



to j'ou and sacrifice a certain for a doubtful happiness ? 

 I could not have yielded to such a suggestion without 

 dishonour to myself and misery' to us both." 



He then relates how in accordance with Turia's own 

 desire he had adopted a daughter, and this is how the 

 long inscription ends : 



" I might dwell on all j-our forethought and good 

 counsel, but I must reserve this space rather for a 

 tribute to your goodness, so that at least I may show 

 how deeply I lament the wife whose memory I have 

 sought to consecrate for ever. Do not think that your 

 example will be forgotten, for your fair renown meets 

 me at even,- turn and teaches me to be brave against 

 ill-fortune. Fate has not robbed me of everything since 

 it still suffers me to cherish the memory of your good- 

 ness, though I have lost all the peace of my soul in losing 

 you. ^^'hen I think how you were wont to foresee and 

 provide against my dangers, I am broken down with the 

 thought of my calamity, and I cannot be faithful to my 

 promise not to grieve. Grief overcomes my resolution, 

 and I am plunged in sorrow whether I look forward or 

 backward ; and the ver>- greatness of your memory 

 makes the rest of my life promise nothing but days 

 of mourning. My last \\-ord shall be that there was 

 nothing which your goodness did not deserve, but that 

 I never succeeded in paying my debt. I have counted 

 your last commands as a law, but I will spare no honour 

 which they did not forbid me to render you. And now 

 I pray that the gods with whom your spirit is give 

 you peace now and for ever." 



The Study of Plankton 



By J. Travis Jenkins, D.Sc, Ph.D. 



M.\RINE organisms can be roughly divided into three 

 groups according to their mode of life ; the plankton ' 

 or drifters, the nekton or swimmers, and the benthos - 

 or fixed organisms. The division is verj' convenient 

 for students of marine life, but it must not be pressed 

 too far, since many animals and plants belong to one 

 group at one stage of their life-history, to another 

 group at another stage. To the first group, the 

 plankton, belong all those creatures which, owing either 

 to their small size or feeble muscular development, are 

 unable to make any headway against a current, but 

 drift about at the mercy of the wind and tide. Only 

 quite recently has the importance of this group been 

 recognised ; it is now generally regarded as the source 

 of all organic matter in the sea. 



Nearly all marine animals or plants are represented 

 at some stage or other of their life-history in the 



' Literally, "tossed (by the waves)." 



- Literally, " the great depth." 



plankton. Life swarms in all the surface layers of 

 the ocean that are penetrated by sunlight. This 

 life depends ultimately on the power which marine 

 plants possess of manufacturing organic substance from 

 inorganic by means of their chlorophyll corpuscules, 

 the energy being supplied by sunlight. Most people 

 have an erroneous idea of marine plant life. The 

 floor of the ocean is not covered with marine forests. 

 Only along the comparatively limited area of the littoral 

 zone is there any growth of fixed marine plants. By 

 far the greater quantity of marine plants are micro- 

 scopic in size, they float in the surface layers and conse- 

 quently belong to the plankton. They are the true 

 pastures of the sea, and upon their abundance all 

 animal life depends, including our food fish of economic 

 importance, and, consequently, our great sea fisheries. 



There is therefore no reason for surprise that the 

 plankton has been extensively studied during the last 

 decade or so, and voluminous works have been pub- 

 lished dealing with this branch of marine biology. 

 The plankton group is of enormous extent and astound- 

 ing variety. The skeletal remains of former planktons 

 form vast deposits on all the ocean floors. These 

 planktonic deposits are found nearly everywhere, except 

 where the solvent action of the salt water has removed 

 the bulk of the skeletal remains. The various oozes — 

 Diatomaceous, Radiolarian, and Globigcrina — are de- 

 rived from the remains of planktonic organisms. 



The abundance of the vegetable plankton depends on 

 the presence of certain chemical elements in the sea- 

 water. WTiere these elements are present in the 

 greatest abundance the plankton is richest. 



Many open-sea fish live directly on the plankton. 

 These plankton-eaters, which include the herring, 

 sprat and mackerel, are provided with comb-like 

 structures — the gill-rakers — which arc attached to the 

 gills and act as food strainers. 



When the fish breathes, water is taken through the 

 mouth and passed out over the gills, and during this 

 process minute organisms of the plankton are retained 

 by the gill-rakers, whence they are washed off by the 

 fish's tongue and swallowed. If the contents of the 

 stomach of an open-sea fish such as a mackerel be 

 examined, they will be found to consist of planktonic 

 Crustacea ; as, for instance, the young of the hermit 

 crab, the second stage in the development of the 

 Norway lobster (Neplnops) and prawns (Palinurus). 



The various organisms met with in the plankton are 

 now well known. Not only have they been identified 

 and described, but chemical analyses of the group 

 have been made and comparisons with land animals 

 and plants instituted. We have already noted that 

 nearly all marine animals are represented in the 

 plankton at some stage or other of their life-history. 

 Fish are found in the egg and larval stage. With the 



