352 



SCIENCE 



[N. S. Vol. XL. No. 1027 



they are all necessary." And thougli we are 

 prone to consider the last determining condi- 

 tion for a process as its cause, in reality " a 

 state or process is solely determined by the 

 sum total of its conditions." Living material 

 by virtue of its irritability adapts itself to 

 changes in the conditions of its existence, by 

 various manifestations with which we are fa- 

 miliar. "Life is the entire sum of the vital 

 conditions." 



A stimulus is every alteration in the vital 

 conditions, being a stimulus only when con- 

 sidered in relation to the previously existing 

 state. The alteration may be subliminal, min- 

 imal, submaximal, or maximal; it may be 

 harmless or injurious ; short, long or the initia- 

 tion of a new condition which is to persist. 

 Since there are certain internal vital condi- 

 tions that are always undergoing change, as in 

 development, and external vital conditions that 

 may exist unchanged, and independent of the 

 vital process, a suggestion is made that for 

 practical purposes stimulation be defined as 

 " every alteration in the external vital condi- 

 tions." 



Having achieved the new viewpoint (and 

 indeed the word " new " might be omitted, for 

 most of us have none), the reader follows 

 through equally lucid discussions of the char- 

 acteristics and effects of stimuli, of the process 

 of excitation, of conductivity, the refractory 

 period, fatigue, interference and states of de- 

 pression, meeting old facts in unexpected 

 places, watching isolated observations falling 

 into line, and finding new meanings in all that 

 is placed before him. 



To suggest that the book be read for pleas- 

 ure is perhaps apparently to belittle its impor- 

 tance. If so the fault lies in the general no- 

 tion of the meaning of pleasure. But it is un- 

 doubtedly true that the biological scientist has 

 few such opportunities for simultaneously pur- 

 suing happiness and acquiring merit. 



The reviewer had almost forgotten to refer 

 to the excellence of the translation, for which 

 the author makes gracious acknowledgment. 

 The reader will find it very easy to forget that 

 the book was not originally written in English. 



c. c. s. 



REGENEMATION OF ANTENNA 



Some interesting results have been achieved 

 by experiments, made and reported by H. O. 

 Schmit-Jensen,^ on the regeneration of severed 

 antennffl of Phasmidae. A rather large number 

 of small and half-grown larvae of Dixippus 

 morosus had been insufficiently supplied with 

 fresh vegetable food and thus cannibalism 

 appeared among them, and a number were 

 found with one or both antennae or some of 

 their limbs missing. A single specimen at- 

 tracted attention because of one of its attennse 

 having regenerated like a little loot. After 

 the following molt this organ had increased 

 in size and became still more foot-like in form. 



This case of spontaneous homoeosis caused 

 the author to cut the antennae from fifty newly 

 hatched and sixty half -grown Dixippus larvae, 

 all the larvae being from unfertilized eggs. 

 The antennae were severed between the first 

 and second segments or between the second 

 and third, sometimes the left antennse being 

 cut and sometimes the right and in some cases 

 both were amputated. When both were cut 

 the specimens died. In some cases where the 

 single antenna was severed there was no 

 regeneration, only a knot developing. But 

 often there was produced, not a small antenna, 

 as one might expect, but a tarsus consisting of 

 from one to the normal five segments com- 

 plete with terminal claws with the ordi- 

 nary arolium between them. In four cases 

 a tibia was also developed. In young larvas 

 there seemed to be a distinct increasing 

 development of the foot-like characters of the 

 regenerated organ with each molt. After the 

 first molt succeeding amputation there ap- 

 peared only a short knob. The next molt pro- 

 duced a segment with evident claws and the 

 third molt brings the organ into more perfect 

 tarsal formation. Some of the more perfect 

 tarsus-like regenerations are, as shown by 

 figures' reproduced from photographs, almost 

 indistinguishable from an actual foot, some, 

 as stated above, even having the tibiae present. 

 In the older larvae the place of severance 



1 Meddel. fra DansJc naturh. Foren., Vol. 65, pp. 

 113-134, Figs. 1-7 (1913). 



