586 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pearl Oysters.* — James Hornell reports some interesting and im- 

 portant observations on the pearl oyster banks of Ceylon. He is still in 

 search of the adnlt stage of the pearl parasite. He confirms the theory 

 set forth by Professor Herdman and himself that shell-pearls with no 

 vermean nucleus are especially associated with the attachment surfaces 

 of those muscles which have insertion on the shell, especially the small 

 and comparatively weak levator and pallial muscles. Some remarkable 

 illustrations of the activity of the young pearl oysters are given. The 

 effects of this remarkable restless activity are two-fold : it gives a 

 younger generation great advantage over an older in the struggle for 

 existence, the young ones mounting on the topmost parts of the older 

 ones and intercepting food particles which otherwise would pass to the 

 latter ; and it aids them also in finding elevated places of refuge when 

 an influx or disturbance of sand occurs. Attention is called to a remark- 

 able phosphorescent phenomenon, previously witnessed by Herdman, 

 " as if the sea were swept by regularly recurring searchlight rays," at 

 intervals of about two seconds and lasting for an hour, each evening. 

 The cause remains undetermined. The bulk of the report is of course 

 strictly practical. 



Arthropoda. 



a. Insecta. 



Notes on Insect Bionomics.t — V. L. Kellogg and R. G. Bell have 

 made various experiments on silkworms. Alterations in the food condi- 

 tions show that individuals living through their whole post-embryonic 

 life on the smallest food supply capable of sustaining life, a supply 

 varying from one-fourth to one-eighth of the supply normally used by 

 individuals of the species, do not necessarily become males. Silkworms 

 may be cut off from a food supply nearly seven days before the normal 

 limit of their feeding time, and yet complete their development quite 

 normally. The deprivation of food for from one to four days seems 

 neither to hasten the metamorphosis nor to modify it appreciably, nor 

 to result in the production of a moth of lessened size or lessened fertility. 

 If the larva? are deprived of food for eight days or more before their 

 normal spinning-up time, they invariably die without forming a cocoon, 

 and in only one case was pupation accomplished. A silken cocoon loses 

 a very small amount, about 4 p. a, of its weight in the first day after its 

 completion, and then loses no further weight. The pupa loses weight 

 slightly but persistently and steadily from day to day throughout its 

 entire duration, the total loss amounting to about 14 p.c. The pupa? of 

 the tent caterpillar (Clmocampd), of the checker-spot butterfly (Melitcea), 

 and of the mourning-cloak butterfly {Euvanessa antiopa), also lose 

 steadily in weight from day to day, the total loss being from 35 to 

 65 p.c. 



Phylogeny of Insects.J — Anton Handlirsch makes a statement of 

 his conclusions as to the phylogeny of insects, which result in the 

 following arrangement : — 



* Keports from Ceylon Marine Biol. Lab., No. 1 (Colombo, 1905) pp. 1-39 (15 pis., 

 maps, and tables). t Journ. Exp. Zool., ii. (1905) pp. 357-67. 



X SB. K. Akad. Wiss. Wien, cxii. (1903), received 1905, pp. 716-38 (1 table). 



