416 NOTES. 



for those made on domestic animals can scarcely be regarded as such, 

 since their results cannot be considered applicable to other animals 

 living in a state of nature. Sanson has lately made some very interest- 

 irg experiments on domestic animals, which seem to prove that sexual 

 maturity can be very much hastened by a careful and special hygiene, 

 by an increased amount of nourishment and by the addition of certain 

 substances to the diet. (Sanson, Comptes Rendns, 1874, Ixxix. 1768; 

 and Journal de V Anatomic et de Physiologic, 1872, p. 113.) The animals 

 thus brought up are said to assume a quite special development to 

 become races ; the signs of their earlier development and precocious 

 maturity are the cutting of the permanent teeth and the growing 

 together of the epiphyses (the osseous portions of the hollow bones) at 

 an age when, in animals fed in the usual manner, these tokens of 

 approaching maturity are not yet visible. As we shall presently see, 

 precisely similar effects follow from raising the temperature. In con- 

 clusion I will only mention that Von Willich states that in frogs a defi- 

 ciency of food causes darker colouring of the skin. 



CHAPTER III. 



Note 16, page 70. A comparison of the eye of the animal and the 

 chlorophyll bodies of plants as standards of equal value for estimating 

 the intensity of light was, in fact, attempted by Prillieux. Sachs has 

 controverted this attempt in his usual brilliant and thorough way, and 

 has set it aside, let us hope, once for all. 'All comparisons as to the 

 intensity of differently composed light, made by means of the eye, 

 have, from the nature of the eye, no independent value.' Hence the 

 intensity of the different colours of the spectrum as thus estimated can- 

 not be made use of to measure the gas disengaged by plants by means 

 of the chlorophyll bodies, as Prillieux has done. 



Note 17, page 72. I here give a complete list of those species of 

 animals in which chlorophyll or similar bodies as xanthophyll, &c. 

 are said to occur, 

 otozoa : 



Etiglena viridis. 

 Steiitor viridis. 



Almost all Radiolaria. But among the marine Eadiolaria most of 

 the Acantho-metridae are excepted (Haeckel, Monograph of the Radio- 

 laria); and among the fresh- water Eadiolaria, ActinopJirys, Actino- 

 spha>riwn, &c. 



