44 



SCIENCE 



[N. S. Vol. XLIX. No. 1254 



"La Variegana (Olethreutes vanegdna Eh) 

 ed I Suoi Parassiti." Tlie observations to 

 which especial attention should be called in 

 this connection are likely to be unnoticed by 

 students of polyembryony, and this especial 

 note is therefore written. 



One of the parasites of Anarsia lineatella is 

 Encyrtus variicomis Nees, a species not known 

 to the present writer, but which was retained 

 in the genus Encyrtus by Gustav Mayr in his 

 monograph of the European Encyrtidse. The 

 only previous record of its rearing seems to 

 have been by Nees, from a cell of Eumenes 

 coarctaia, and it now appears from the obser- 

 vations of Sarra that it is altogether likely 

 that IsTees's specimen came not from the larva 

 of the Eumenes but from some lepidopterous 

 larva stored in the cell. 



Sarra finds that the female parasite lays 

 eggs in the egg of the Anarsia; that the para- 

 site egg gives origin to a number of larvae 

 which live within the larva of the Anarsia 

 after it has hatched, in just the same way as 

 do the other related larvae as studied by 

 Marchal and Silvestri. 



The second case is that of an unnamed 

 species of Copidosoma reared from the larva 

 of Olethreutes variegana. Here too, the para- 

 site eggs are laid in the egs of the Olethreutes 

 and develop in its larvae, 68 females and 80 

 males being reared from a single host larva. 



These observations are of interest not only 

 as adding two species to the list of polyem- 

 bryonic forms, but, since Encyrtus variicomis 

 has not previously been associated with the 

 Copidosoma and Leptomastix group of En- 

 cyrtidce, another genus is added to the list. 



L. 0. Howard 



tion " was erroneously attributed to Bertrand 

 Russell. It should have been attributed to 

 Professor C. J. Keyser'^ who is the originator. 



"With reference to the criticisms by Pro- 

 fessor Franklin and MacNutt, in Science of 

 November 8, of my communication of October 

 4, I do not merge " identification " and 

 "measurement," in the paper mentioned, but 

 state that I think the distinction between 

 them valueless in the context referred to. 

 So far as the relation between mass and force 

 is concerned, I was merely following Messrs. 

 Franklin and MacNutt's words: "We prefer 

 to define mass quantitatively (italics mine) 

 in terms of the operation of weighing by a 

 balance scale.'' ITothing other than a quan- 

 titative definition would be of value in the 

 equation f/a = m. 



The fimdamentally defining quantities need 

 not be the same as those kept by the Bureau 

 of Standards. Temperature — the real tem- 

 perature — is defined by Carnot engines, but 

 they do not keep Carnot engines in the Wash- 

 ington bureau. Chemical affinity as measured 

 with the help of a Weston standard cell is 

 another example of the same thing. The veri- 

 fication comes from the totality of physical 

 experience. " An experiment," says Duhem,^ 

 can never condemn (or validate) an isolated 

 hypothesis but only a doctrine {ensernble 

 theonque." 



Of course, there are other kinds of physics 

 besides force physics, and it would be erro- 

 neous to say that any of the discussions ex- 

 hausted all there is in the ideas of force, mass, 

 etc. 



Paul J. Fox 



1203 Stock Exchange, 

 Philadelphia., Pa. 



FOUNDATIONS OF MECHANICS 



In a communication to Science of October 

 4, I used the term " doctrinal function " in 

 the sense of a consistent body of postulates 

 and theorems containing one or more unde- 

 fined elements, but considered apart from any 

 of the various interpretations that could be 

 placed on the undefined elements. The intro- 

 duction of this useful term " doctrinal f unc- 



TROPICAL ENERVATION 



The opinion is widespread, in northern 

 climes, that a continuously warm climate, im- 

 broken by sharp periodic changes, is ennervat- 



1 See Keyser, ' ' Hmnan. Worth of Eigorous 

 Thinking," p. 254, and "Doctrinal Functions," 

 Jour, of Philos., Psychol, and Sci. Methods, Vol. 

 XV., p. 262. 



2 " La Thfiorie physique, ' ' Paris, 1906. 



