RECORDS OF MEETINGS OF 1907 361 



the egg, although its polar rays may suffer to some extent by prolonged 

 centrifuging. Under the pink cap and concealed by it in the living egg is a 

 vesicular material that is the nuclear sap of the ovarian egg. The polar 

 bodies may appear at any point of the surface of the egg, so far as the loca- 

 tion of the three zones is concerned. It is probable that the spindle comes 

 to the same pole as in the normal egg. Since the eggs are not oriented as 

 they fall any one of the three kinds of materials may lie at the "animal 

 pole." 



The cleavage always begins beneath the polar bodies, as in the normal 

 e^g, and the cleavage pattern, the size of the cells, and their tempo of divi- 

 sion are exactly that of the normal. All of the yolk, for example, may be 

 contained in the small cell of the first two, yet the size of this cell and its 

 rate of division are not thereby affected. 



It follows that in this egg the determinate type of cleavage is not caused 

 by the distribution of the visible substances of the egg. Sections show that 

 between the time of centrifuging and the appearance of the cleavage planes 

 the induced distribution is to a large extent retained, the amount of dis- 

 turbance depending on the length of time elapsing and on the location of 

 the polar spindle, etc. The results confirm observations on the living egg, 

 and show that the yolk or the pigment may go largely or entirely to one of 

 the first formed cells. 



The centrifuged eggs produce swimming embryos, and in some cultures 

 a large percentage of such embryos. Until isolation experiments have been 

 successfully carried out it is necessary to speak with some reserve concerning 

 the percentage of normal embryos. 



In the sea urchin egg, Lyon has sho^n that the cleavage follows the 

 induced stratification, while in Cumingia this is not the case. The difference 

 is due to the shifting of the nucleus in the egg of the sea urchin, while the 

 spindle in Cumingia retains its original orientation. 



Dr. Osbum said, in brief : The specimen in question is a male of Syrphus 

 arcuatus Fallen (Diptera), a common and widely distributed species, and 

 was collected at Montreal, Canada, by Mr. G. Chagnon who noted nothing 

 unusual in its behavior. The right side of the head is normal, but on the 

 left side the large compoimd eye is entirely wanting. A third antenna 

 appears on this side of the head posterior to the normal left antenna and 

 entirely separated from it, occupying a fossa of its own. It is normal in 

 structure except that the arista, or dorsal bristle, is undeveloped, and it is 

 slightly smaller than the normal ones. This condition calls to mind Herbst's 

 experiments in Crustacea (Palcemon, Sicyonia) where an antenna developed 

 in regeneration after the excision of the eye, but no similar case is known 

 among insects as far as the writer is aware. It is possible that the eye may 



