390 SUMMARY OF CUllEENT RESEARCHES RELATING TO 



to be mainly due to changes in temperature and food. The rarely- 

 appearing discontinuous variations were apparently not inherited. 



Brain of Termites.* — Thompson finds that the structure of the 

 brain in termites is very like that in ants, except that the mushroom- 

 shaped bodies are much simpler and more primitive. No sex differen- 

 tiation occurs between the brains of the different castes or stages, and 

 but little caste differentiation appears, although the optic apparatus 

 shows a correlation between the degree of development of the compound 

 eyes and the size of the optic lobes. Simple ocelli are present in the 

 nymphs and adults of the sexual forms, absent in the worker and 

 soldier. The problematical frontal gland, which seems to be functional 

 only in the true adults and soldiers, may be derived from the ancestral 

 median ocellus. 



Growth and Habits of Stick Insect-f — H. Ling Roth has made a 

 study of the growth and habits of the stick insect, Garausius morosus Br., 

 as a contribution towards a knowledge of variation in an organism which 

 reproduces parthenogenetically. The observations were made in a 

 regulated temperature from SC-GJ:" F. The insects, which are lethargic 

 in habit, vary in colour from light fawn to dark green. Occasional 

 very dark brown examples occur. During life the colour barely changes. 

 Incubation in boxes varied from 137-2'J7 days. The insects were 

 parthenogenetic ; only one, obviously an infirm female, failed to produce 

 eggs. One male was found, but it had no contact with any of the 

 females under observation. The average length of egg-capsule was 

 2 • 8 mm. Under 2 * 6 mm. they did not hatch out. The fertility of the 

 eggs was 81*5 p.c. Eggs are dropped on an average 16*5 days after 

 the last ecdysis. The average egg-production was 513 per insect, the 

 highest total reached by one insect being 712. No correlation could be 

 found between the length of the insect and the number of eggs. The 

 length of the nymphs on hatching averaged 10*5 mm., and in twenty- 

 one days they had increased .3-5 mm. This is the only period during 

 which they grow without moulting. The nymphs fast from 2-6 days 

 before the actual moult. The ecdyses were performed by the nymph 

 hanging head downwards, the skin splitting from the pronotum upwards, 

 when gravity did the rest. There were six ecdyses in each case, 

 and the increase in length each time was very marked. The body- 

 length increased six-fold ; the antennee increased in the same total 

 ratio, but there were differences of increase in the various segments. 

 The progeny from eggs dropped late in life attained a greater length 

 than that from eggs dropped early. The insect spends two-fifths of its 

 life in the preparatory period (to the sixth moult), and the remaining 

 three-fifths in the reproductive period. 



The author's results bear out the observations of Warren rather than 

 those of AVeismann. Summaries of the variations noted are given 

 in tabxilar form. 



* Journ. Compar. Neurology, xxvi, (1916) pp. 553-603. See also Trans. Amer. 

 Micr. Soc, XXXV. (1916) pp. 266-7. 



t Trans. Entomol. Soc. London, iii.-iv. (1916, publ. 1917) pp. 345-86. 



