286 



SCIENCE 



[Vol. LVI, No. 1445 



intermediaries. Here, however, is a chain of 

 two links, obviating the necessity of the "mid- 

 dle man," and five words tell a complete story: 

 "No diatoms, no gizzard shad." In some fishes 

 from Ohio another story is told by changing 

 diatoms to Pediastrum; still another, if one 

 puts in Scenedesmus; for most of the young 

 fishes examined the complete story reads : "No 

 phytoplankton, no gizzard shad." 



4. Flagellate forms, species of Euglena and 

 Phacus in particular, are less common in the 

 Ohio fishes. 



5. The relative abundance of the different 

 forms of the phytoplankton of the bodies of 

 water is revealed by the algal content of the 

 gizzard shad found there. 



6. In general, algal species belonging to the 

 order Protococeales form more commonly a 

 larger portion of the food of the gizzard shad 

 than do either flagellates or diatoms. Some- 

 times, however, the condition is reversed; but 

 this is apparently purely a matter of the plank- 

 ton content of the water. 



7. The fewness of ithe zooplankton forms is 

 somewhat less marked in the specimens from 

 Illinois than in those from Ohio. This may 

 again be due to the predominance of the phyto- 

 plankton over the zooplankton in the localities 

 where the fish were obtained. 



8. The paucity of stream phytoplankton in 

 comparison with that of ponds and lakes is 

 shown by the relative algal content of the diges- 

 tive tract of the gizzard shad taken from run- 

 ning and quiet waters. The excessive diatom 

 content of stream water at certain periods — 

 producing the so-called "pulses" of Kofoid' — 

 when there is a marked rise in temperatui-e is 

 only temporary and may be explained, as Pro- 

 fessor Transeau suggests, by the rapid dis- 

 solving of the mucus and a consequent break- 

 ing up of the chains and colonies of diatoms. 

 This usually takes place in the small tributaries 

 where the individual diatoms are thus freed 

 from their places of attachment; and the main 

 stream is merely the recipient of the contribu- 

 tion, not the source of the sudden "pulse." 



9. There is a continuation of the above story 

 in which the gizzard shad plays an important 



3 Bulletin of the Illinois State Laboratory of 

 Natural History, 6, pp. 226, 569, 571, 1903. 



role : it feeds the game fishes, and the game 

 fishes feed man. Thus, the gizzard shad is 

 making useful for man the energy stored in 

 plant forms which occupy no land areas, which 

 do not interfere with the ordinary disposition 

 or utilization of bodies of water (except the 

 occasional contamination of water for drinking 

 purposes by some algas), which involve no 

 labor of cultivation on the part of man, and 

 which are of no value for direct human con- 

 sumption. 



10. The world's population in the last hun- 

 dred years has increased about 150 per cent. 

 Along with this increase has had to come a 

 corresponding increase in the world's food sup- 

 ply. One of the ways in which this necessity 

 has been met is the seciu'ing of new acres of 

 soil in which to grow crops. It is easily seen, 

 however, that there is a limit to new acreage. 

 In the future, therefore, we may have to turn 

 more of our attention to the cultivation of the 

 waters for food supplies. We may have to 

 develop an industry of aquieulture as we have 

 developed an industry of agriculture. The time 

 is rapidly approaching when fish will be more 

 highly prized as food and more extensively 

 used than now. As that time comes, the cul- 

 tivation of algEe will be a fii-st step toward 

 greater fish production. A second step may 

 be the introduction of fish like the gizzard 

 shad into fish ponds and lakes to make more 

 readily available the phytoplankton for fish 

 food. 



L. H. Tiffany 



The Ohio State Universitt 



THE SEX CHROMOSOMES OF THE MONKEY^ 



Previous studies on the spermatogenesis of 



the opossum ('22) and on man (in press) have 



1 Contribution No. 159, Department of Zoology, 

 ■University of Texas. The present work has been 

 aided by a grant from the National Research 

 Council — Committee for Researcli on Sex Prob- 

 lems. In view of the crowded condition of our 

 journals which greatly delays publication, the 

 author is presenting in this brief way the essential 

 facts of general interest to biologists. The com- 

 pleted stud}' will give the detailed evidence. 

 Painter, T. S. : 1922, ' ' The Spermatogenesis of 

 the Opossum," Journ. Exp. Zool., Vol. 35. 



