RECENT ADVANCES IN SCIENCE 399 



intensity and direction of these beams, the direction of action 

 being given by the resultant of a " parallelogram of forces," in 

 which the direction and length of the sides represent the direc- 

 tion and intensity of the beams at their place of action. The 

 same law can be applied to the case of a number of beams 

 acting in different directions. 



In the case of the blue-green algae Nienburg {Zeitsch. f. Bot. 

 8, 161-93, 191 6) shows that the whole thread is equally sensitive 

 for the perception of light stimulus. The response to the 

 stimulus takes the form of alteration in velocity, the movement 

 slowing down with small light intensities and increasing with 

 high intensities. A sudden change from light to darkness brings 

 about reversion of the direction of movement, but the reverse 

 change has no effect on the direction of movement. It has 

 been shown by Harder (Zeitsch. f. Bot. 10, 177-244, 191 8) that 

 stimulation of the Nostocaceae by mechanical means such as 

 pressure against an obstacle, or by sudden transference from 

 light to dark, also results in a reversal of the direction of move- 

 ment. 



In conclusion mention may be made of some recent work 

 by Miss Parr (Ann. of Bot. 32, 117-205, 191 8) on the respoiise 

 of a fungus, Pilobolus, to light, in which a curvature of the 

 sporangiophores results from light stimulation. The response 

 takes place to rays of all parts of the visible spectrum, but has 

 a marked relation to wave frequency. The presentation time 

 increases gradually from the violet to the red end of the spec- 

 trum, an observation confirming Brefeld's earlier results. The 

 presentation time multiplied by the square root of the frequency 

 gives a product which is nearly constant, but which decreases 

 slightly and gradually with increase in frequency. The pre- 

 sentation time is related to the spectral energy approximately 

 in accordance with the Weber- Fechner rule, " if the wave 

 frequencies are made a function of the constant." 



ZOOLOGY. By Prof. Chas. H. O'Donoghue, D.Sc, F.Z.S., University 

 of Manitoba, Winnipeg, Canada. 



Invertebrata. — Bourne has published an interesting paper " On 

 Some New Philliinse from New Guinea " (Quart. Jour. Micro. 

 Sci. vol. lxiii, 63, April 191 8). The scope of the paper, how- 

 ever, is hardly indicated by its title, for, in addition to providing 



