April 6, 1900.] 



SCIENCE. 



555 



NECTURUS MACULOSUS EAFINESQUE IN THE 

 LOWER DELAWARE RIVER. 



In the American Naturalist for 1892, pp. 779 

 and 780, Mr. W. B. Marshall gives au account 

 of ' Necturus maculatus in the Hudson River ' in 

 which he calls attention to the fact that no record 

 is known to him of its inhabiting the Delaware 

 Eiver, though he presumes that it may pi-ob- 

 ably be found there at some future time. I am 

 very glad to justify his statements with the fact 

 that I have received a mature living specimen 

 for examination that was taken in Darby Creek, 

 which is a tributary of the Delaware River and 

 into which it empties several miles below Phila- 

 delphia. The precise locality was near Essing- 

 ton and the date of capture March 2d. When 

 captured, being taken in a small cast net, it 

 was said to have emitted a cry very much re- 

 sembling that made occasionally by frogs when 

 taken in the hand. The animal has now lived 

 a week in captivity and has been feeding al- 

 most entirely on small fish and tadpoles. It 

 seems particularly fond of the common Mud 

 Minnow (Umbra pygmasa) and various small Sun- 

 fishes (Centrarchidse), of which it has consumed 

 about fifty or more. By the occurrence of this 

 species in the lower Delaware, where, it would 

 seem, it found its way from the Hudson River 

 by means of the Delaware and Hudson canal, 

 which connects the two rivers at Port Jervis 

 and Kingston, it has enlarged its geographical 

 distribution through the unintentional aid of 

 man. Most likely the occurrence of other 

 aquatic animals, indigenous to the western 

 part of New York, that have or might be found 

 in the Delaware basin, have reached the latter 

 through the same means, as the Erie canal con- 

 nects the Hudson with many of the streams 

 of western New York. 



Henry W. Fowler. 



lampreys in captivity. 



Very small (6 mm. -8mm.) Ammocoetes larvse 

 are quite delicate, and it was only by the exer- 

 cise of the greatest care that they were kept 

 alive, in aquaria, for a period of six weeks. 



Older larvse (10 cm. -15 cm. in length), on 

 the other hand, are remarkably hardy, and may 

 be kept alive indefinitely in small aquaria of 

 running water. It is not even necessary to 



have a constant changing of water. Sand 

 should be placed in the aquaria, in which the 

 larvae may bury themselves. 



The adult lampreys are moderately hardy 

 and may be kept in small tanks of running 

 water without difficulty. By catching a number 

 of the adults, in the spring, as they are passing 

 up the rivers to the spawning grounds, and 

 keeping them in captivity until sexual maturity 

 is reached, it seems probable that artificial fer- 

 tilization may easily be accomplished and em- 

 bryological material thus obtained. 



Albert M. Reese. 



Johns Hopkins University. 



NOTES ON PHYSICS. 



THE rationalism OP ELECTRICAL UNITS. 



Present electrical units are irrational in that 

 the factor 4- does not appear in certain equations 

 where it would be proper for it to appear, while 

 in other equations this factor does appear im- 

 properly. The British Association Committee 

 on Electrical Standards fixed for us the present 

 definitions of the units of magnetism and of 

 electric charge when they published in one of 

 their reports the little treatise on units by Max- 

 well and Jenkiu. In this treatise the factor 47r 

 is suppressed for the sake of simplicity and the 

 result is that we have an ' eruption of 47r's ' in 

 other quarters. This eruption is due, literally, 

 as Heaviside puts it, to the wisdom of our an- 

 cestors, who, according to the same witty sage, 

 were suflflcieutly wise in their generation. 



Several proposals have recently been made 

 looking to the rationalization of our electrical 

 units. The complete solution of the difiiculty, 

 according to the wisdom of the present genera- 

 tion, is proposed by Heaviside. This proposal 

 involves great changes in the magnitudes of all 

 electric and magnetic units — a very serious 

 matter. 



Professor Fessendeu proposes an ingenious 

 solution of the diflieulty which involves no im- 

 portant change in any of the units which are 

 used by engineers. Professor Fessenden's so- 

 lution does not, however, completely rid us of 

 the irrational appearance of the 4^ factor, and 

 if this solution were to be adopted by us, our 

 posterity might still suffer by our wisdom. 



