346 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The second generation of adults emerge about the same time as 

 those of the previous species. They utilize the very young larval 

 hosts for oviposition, only one egg being laid in each Coccid. The 

 larval parasites winter in the apneustic condition in their hosts. A 

 partial third generation of adults has been observed. 



The results of the first generation of parasitism on the host are 

 economically negligible for both species. The hosts do not succumb 

 until after they have deposited their ova. The effects of the second 

 generation of parasitism are complete ; about 40 p.c. of the hosts are 

 attacked and destroyed a long time before attaining sexual maturity. 

 The second generation limits the abundance of the host, and keeps 

 it from becoming a pest, notwithstanding its high fecundity. J. A. T. 



Somatic Mitosis of Stegomyia fasciata. — Lucy A. Carter {Quart. 

 Journ. Micr. Sci., 1918, 63, 375-86, 1 pi.). The development of the 

 eggs of this mosquito is very rapid, the fulfilment of a condition necessary 

 for the successful study of somatic mitosis, in order that a copious 

 supply of dividing nuclei may be secured in a single specimen, thus 

 rendering the seriation of stages possible. The present investigation 

 had for its immediate aim to discover whether there is a pairing of the 

 chromosomes in the somatic tissues. The diploid or normal number 

 of chromosomes is four. A varying degree of parasyndesis (pairing of 

 the chromosomes) is exhibited in the somatic cells, extreme cases giving 

 the haploid (or " reduced ") number. Each telophasic (i.e. at the close 

 of mitosis) mass of chromatin gives rise directly to a synizetic nucleus 

 (i.e. with a clumping together of the chromatin) instead of the usual 

 " resting " nucleus. The nuclear membrane''persists throughout mitosis. 

 The homologous chromosomes pair either in anaphase or in telophase. 



J. A. T. 



Seashore Diptera. — J. W. Yerbury {Journ. Marine Biol. Association, 

 1919, 12, 141-5). An annotated list of Diptera collected near Plymouth 

 which spend a considerable part of their existence in salt or brackish 

 water. They are grouped according to their surroundings — in salt-water 

 pools, on wet rocks, under dead seaweed, on wet sand, on dry sand, on 

 mud flats, in salt marshes, and so on. A few forms may be named : — 

 Clunio marinus, Aphrosylus raptor, Scatophaga litorea., Fucomyia frigida, 

 Cliersodromia cursitans, Hydrophorus bisetus, and Hydrophotiis bipunc- 

 tatus. J. A. T. 



Lecture on Pleas. — G. H. Rodman {Photomicrographic Journal, 

 1919, 8, 2-19, 4 figs.). A flea like that of the mole has been obtained 

 in Eocene amber. Opinion inclines in favour of a special order, 

 Siphonaptera. The eggs are at first sticky and adhere to the substratum 

 on which they are laid. The larvse hatch out in two to ten days. The 

 egg-opener is lost after the first moult. The caudal stylets of the larvae 

 are used as props in creeping and wriggling. After fifteen to twenty 

 days the larva spins a cocoon, including in the wall some debris. In 

 about seventeen days the adult flea emerges. In Pulex irritans the 

 adult can live for a long time (100 days in experimental conditions) 

 without food ; in the European Rat Flea {Ceratophyllus fasciatus) a 

 month is about the limit. After pairing, the female usually requires a 



