ZOOLOGY AND BOTANY. MICROSCOPY, EL'l!. 293 



triad includes the proventricular, the oesophageal, and the supra- 

 pharyngeal-clypeal metameres. The second or cerebral triad includes 

 the protocerebral, labral, or ocular, the deutocerebral or antennary, 

 and the tritocerebral, infra-pharyngeal, or post-antennary metameres. 

 The third or gnathal triad includes the protognathal or mandibular, the 

 deutognathal or maxillary, and the tritognathal or labial metameres. 

 The fourth or thoracic triad includes the prothoracic, mesothoracic, 

 and metathoracic metameres. The fifth triad or first abdominal corre- 

 S[3«)nds to the petiolar area of Myrmicidae, and includes the median 

 metamere of Hymenoptera, the petiolar of ants, and the post-petiolar of 

 Myrmicidffi. The sixth triad is the so-called gaster of Myrmicidje, and 

 includes the fourth, fifth and sixth abdominal metameres. The seventh 

 triad is the female genital area, including the metamere with the female 

 genital aperture, the metamere with the anterior gonapophyses, and the 

 metamere with the posterior gonapophyses. The eighth triad is the 

 male genital area, including the metamere with the penis of Hymen- 

 optera, the metamere with the lateral cerci of Apterygota, and the 

 metamere with the unpaired cercus of Apterygota. The ninth or 

 proctenteric triad, includes the anal, rectal and intestinal metameres. 



Duration of Life and Temperature Coefficient in Drosophila.* 

 Jacques Loeb and J. H. Northop raise the question whether there is 

 a definite coefficient for the duration of life. This might be expected 

 if the duration of life depended upon the presence of certain substances 

 which are used up during life, or if the duration of life were limited by 

 the cumulative injurious effects of certain products of metabolism. 

 Experiments with Drosophila showed a temperature coefficient for the 

 duration of life of about the order of magnitude of that of chemical 

 reactions, namely, of about two for a difference of 10° C. At 28° C. the 

 duration of life in days was 2-4: where the flies were provided only with 

 water, and 7 ' 2 when they were provided with a 1 p.c. cane-sugar solu- 

 tion ; at 90° C. the corresponding figured were 4*1 days and 12 '3 days. 



Nutrition of Insects f— Jacques Loeb and J. H. Northop discuss 

 the question whether the evolution of animals as high in the scale of 

 life as insects was possible without the existence of green plants. Loeb 

 has found that sterile culture media like those used by Pasteur for the 

 raising of yeast were also sufficient for the raising of flies {Drosophila). 

 But the question arose whether the flies might not be carriers of 

 micro-organisms which synthesized the proteins for them. It was 

 found that sterilized flies could not survive in culture media of casein, 

 ■edestin, egg-albumin, milk, and the like. Moreover, flies free from 

 yeast, when raised on sterile bananas or sterile potatoes were also 

 sexually sterile. Yeast seems to be indispensable. Yeast must contain 

 some substance required for the growth of the flies. They can live on 

 any culture medium which can serve as a food for the yeast. They 

 probably infect the food with the yeast. The experiments show that in 



* Proc. Nat. Acad. Sci., ii. (1916) pp. 456-7. 



t Journ. Biol. Chemistry, xxvii. (1916) pp. 309-12. 



