576 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



have a thick wall formed of several epithelial layers, the cells of which 

 are quite irregularly arrangecl, and show signs of degeneration, while there 

 are lacunae between the cells. The yolk-mass is vesicular and spongy. 

 There can be no doubt that we have here to do with a pathological con- 

 dition. Bomhus lapidarius presented just the same phenomena. 



The fourth chapter treats of an increase of surface caused by the 

 development of folds on the inner side of the follicular epithelium of 

 MJtizotrogus solstitialis ; the folds are caused by an invagination of the 

 unilaminar epithelial layer within the egg, and they may extend to the 

 middle of the ovum ; when deep there are never more than three ; it is to 

 be noted that folds and villi are to be seen on the inner wall of the oviduct. 

 Against the supposition that they are abnormal we have to put the fact 

 that they are found in eggs of all stages and of histologically normal 

 character ; nor can they be thought to be due to the faults of preparation. 

 It is possible, then, that the folds are normal and have for their function 

 an increase in the surface of the egg with a view to its better nourishment ; 

 with the growth of the eggs the folds disappear. What happens here 

 cannot but remind us of the numerous folds found by Lankester in the 

 cellular egg-capsule of the Cephalopoda. 



Polar Globules in Insect Ova.* — Dr. F. Blochmann has shown (1) that 

 in five classes of insects the ovum is never without a nucleus ; (2) that in 

 Musca vomitoria, in the winter ova of Aphis aceris, &c., polar globules are 

 formed; (3) that in some parthenogenetic ova at least only one polar 

 globule is formed, while in the normally fertilized two are present. 



In the winter ova of ApJiis aceris two cells are extruded in normal 

 fashion ; the first occasionally gave indications of a nuclear spindle. In 

 two species the summer parthenogenetic ova exhibited only a single polar 

 cell, an observation of some suggestiveness as to the physiological import 

 of these extruded elements. 



In Musca vomitoria a polar globule formation does indeed take place, 

 but the elements are not extruded. Three results of nuclear division 

 remain for a while in a peripheral thickening, the fourth forming the female 

 pronucleus. Polar globules have now been observed in three classes of 

 insects. 



Photogenic Function of Ova of Lampyris.f — Dr. E. Dubois has found 

 that the ova are luminous in ovaries taken from the abdominal cavity of 

 Lampyris, and carefully washed immediately after removal ; the eggs of both 

 fertilized and non-fertilized individuals are luminous, and the development 

 of the light is in direct relation with the degree of intra-ovarial development 

 of the ova. The luminosity persists in laid eggs until the embryo escapes ; 

 the shell abandoned by the larva does not remain luminous, but the creature 

 itself has two luminous organs at the moment of birth ; the luminosity of 

 laid non-fertilized eggs does not last beyond a week, and it has been noticed 

 in eggs in which there is no trace of segmentation. The hygrometric 

 condition of the surrounding medium exercises a great influence on the 

 production of the light, which becomes weakened or extinguished as soon 

 as the moss on which the eggs have been deposited becomes a little dry ; 

 if the dryness has not gone too far, the addition of a little moisture causes 

 the luminosity to reappear. 



Boiling water immediately and alcohol rapidly suppresses the lumi- 

 nosity ; eggs washed and shaken in distilled water do not give up their 



* Biol. Centralb]., vii. (1887) pp. 108-11. 



t P"ll> Soc. Zool, France, xii. (1887) pp. 137-44. 



