108 



SCIENCE. 



[N. S. Vol. III. No. 71. 



In this way, if the observation that after the 

 removal of the old timber in Nevada the water- 

 flow was more even be correct (which I hesitate 

 to accept), it would find explanation in this, 

 that the stumps and roots decayed and thereby 

 increased the channels for the percolatiou of 

 surface waters. 



In conclusion I would say, that geological 

 structure and soil conditions may be such, that 

 percolation takes place readily even without 

 the additional aid of a forest growth, when the 

 effect of the latter may become irrelevant, al- 

 ■ though as a rule it may be accepted as a result 

 of forest removal and exposure of soils, when 

 new growth is at the same time prevented by 

 .fires and by sheep herding, that all soils become 

 gradually more compact and less penetrable ; 

 that then more water goes over the svirface and 

 less remains for subdrainage and that ultimately 

 the change is felt in the riverflow. 



B. E. Peenow. 

 Washington, D. C. 



zoology and biology. 



To The Editor of Science: It is astonishing 

 to find in your columns the assertion, p. 634, 

 that the Johns Hopkins University sends out 

 'Doctors of Philosophy in Biology,' for you 

 might have learned so easily that no such de- 

 gree is known among us. 



The examining board recommends for the 

 degree of Doctor of Philosophy those students 

 who have satisfactorily completed a course of 

 study which this board has previously approved; 

 and among all those who have been recom- 

 mended for this degree during the last twenty 

 years not a single one has presented himself for 

 examination in biology, although many have 

 been examined in various branches of biological 

 science. 



W. K. Brooks, 



Professor of Zoology in the Johns Hopkins Uni- 

 versily. 



Baltimore, April 28. 1896. 



[The criticism of Professor Brooks is directed 

 against a letter signed by Professor Conway 

 MacMillan, of the University of Minnesota. 

 Science is not responsible for the opinions of 

 its correspondents. Ed.] 



THE USE of the TOW-NET FOR COLLECTING 

 PELAGIC ORGANISMS. 



Editor of Science : I have so frequently 

 seen the first use of the tow-net as a means for 

 collecting pelagic organisms placed to the credit 

 of Johannes Miiller that I suspect many zo- 

 ologists are, as I was till recently, ignorant of 

 the fact that Eschscholtz employed the appa- 

 ratus some twenty years earlier than Miiller did. 



In Eschscholtz's ' Review of the Zoological 

 Collection,' appended to the second volume of 

 'A new Voyage round the World,' by Otto 

 von Kotzebue, I find the following on page 327: 

 "The calms near the equator afford an abun- 

 dant harvest to the zoologist, the tranquil water 

 presenting an immense variety of marine ani- 

 mals to his view, and allowing him to take them 

 with little trouble in a net. The open woolen 

 stufl" used for flags oflTers the most convenient 

 material for making these nets, as it allows the 

 water to run through very quickly and does 

 not stick together. A short wide bag should be 

 made of this stuflf, which may be stretched upon 

 the hoop of a cask, and the whole fastened to a 

 loug, light pole. From the height on which we 

 stand above the water it is impossible to per- 

 ceive the smaller animals ; the best way, there- 

 fore, to catch these is to hold the net half in the 

 water, as if to skim off the bubbles of foam from 

 the surface ; then, after a few minutes, if the 

 net is drawn out, and the interior rinsed iu a 

 glass of fresh seawater, one may frequently 

 have the pleasure of seeing little animals of 

 strange forms swimming in the glass. In the 

 course of ten days I obtained, in this way, 

 thirty-one different species of animals." 



Eschscholtz does not tell us exactly when he 

 began this kind of collecting; but the voyage on 

 which he did it was during the years 1823, '24, 

 '25 and 26; and as the above quotation is taken 

 from the account of his observations in the 

 tropical Atlantic before reaching the coast of 

 Brazil, it certainly relates to the earlier part of 

 the voyage. 



In the last one of his series of papers on the 

 development of Echinoderms, published in 1852, 

 Miiller tells us that he had used the tow-net 

 ' vielen Jahren mit dem besten Erfolge.'. The 

 'vielen Jahren,' I suppose, refers to the years 

 during which he was prosecuting his beautiful 



