252 SUMMARY OF CUKBENT RESEARCHES RELATING TO 



by the mediation of a specially differentiated epithelium, the so-called 

 attaching epithelium. This secretes hypostracum and also " epithelial 

 fibrils," each of which is fused at one end with a muscle-fibril and 

 cemented at the other end on to the hypostracum. Each fibril is thus 

 indirectly connected with the calcareous shell. 



Arthropoda. 

 a. Insecta. 



Eyes of Nocturnal Insects.* — E. Bugnion discusses the peculiarities 

 of the eyes of nocturnal insects. Those of Oryctes rhinoceros obliquely 

 illumined at night shine like two rubies. The same phenomenon is 

 seen in Xylotrupes gedeon and Catharsius molossus, and in some nocturnal 

 Lepidoptera. The eyes of Sphinx shine with a reddish colour ; those of 

 some species of Bombyx with a golden yellow. In Sphinx euphorbias 

 the retina is very thick and infiltrated with rose-coloured "erythropsin." 

 Each retinule is divided into a deeper and a more superficial segment, 

 and a retinal tapetum is developed like the choroid tapetum in Mammals. 

 The flat cells filled with crystalloids which reflect the light in the cat, 

 are represented in the hawk-moth by a reticulum of fine trachea? full of 

 air. The reflection is facilitated by a movement of the pigment. The 

 colour is probably due to the erythropsin. It is probable that the light 

 reflected from the tapetum influences the visual cells a second time. It 

 is possible that invisible rays are changed into visible rays in the 

 reflection. 



Germ-track Determinants in a Parasitic Hymenopteron.f 

 Robert AY. Hegner has pointed out in previous studies that in almost 

 every case where an early segregation of germ-cells has been demon- 

 strated in the development of animals, a peculiar inclusion appears in 

 the cytoplasm of the egg at or near the time of maturation. This body 

 finds its way into the primordial germ-cell or cells, breaks up into 

 granules, and becomes distributed among the descendants of the primor- 

 dial germ-cells. These inclusions make the determination of the germ- 

 track possible, and have been called "the Keimbahn-determiuants." 

 Hegner has studied the matter in a poly-embryonic Hymenopteron 

 parasite — Copidosoma (Litomastix) truncatellus, previously investigated 

 by Silvestri. 



A " nucleolus " was described by Silvestri near the posterior end of 

 the egg. But it does not arise from the nucleolus of the germinal 

 vesicle as he supposed. It consists of the entire chromatin content of 

 an oocyte nucleus. Because of its constitution and fate, this body has 

 been named the " Keimbahn-chromatin." Its history is as follows : — 

 The chromatin within the nucleus of the young oocytes seems to form a 

 spireme, which breaks up into chromosomes ; these appear to unite in 

 pairs at or near their ends, and are then drawn upon an asterless spindle : 

 this spindle does not proceed to divide the chromatin, forming two 



* Bull. Soc. Vaud. Sci. Nat., xlix. (1913) pp. xxxiii-vi. 

 t Anat. Anzoig., xlvi. (1914) pp. 51-69 (18 figs). 



