January 10, 1908] 



SCIENCE 



67 



stances ") of the protoplasm are artificially 

 shifted. 



The eggs of Oumingia when laid contain 

 the first polar spindle in the center of the 

 egg. The centrifugal force drives the scat- 

 tered yolk granules to one pole, the pinkish 

 pigment to the opposite pole. Between these 

 two there remains the perfectly clear kineto- 

 plasm, in which the spindle lies, forming any 

 angle with the induced stratification. Its 

 original position has, in fact, been little af- 

 fected by the movement of the other substances 

 through the egg, although its polar rays may 

 suffer to some extent by prolonged centri- 

 fuging. 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 location 

 of the three zones is concerned. It is prob- 

 able 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 egg, and the 

 cleavage pattern, the size of the cells, and 

 their tempo of division 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 hy the distribu- 

 tion of the visible substances of the egg. Sec- 

 tions show that between the time of centri- 

 fuging and the appearance of the cleavage 

 planes the induced distribution is to a large 

 extent retained, the amount of disturbance 

 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 yoll?: 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 per- 

 centage of such embryos. Until isolation ex- 

 periments have been successfully carried out it 



is necessary to speak with some reserve con- 

 cerning the percentage of normal embryos. 



In the sea urchin egg Lyon has shown 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. 

 The Replacement of an Eye hy an Antenna 



in an Insect: Dr. Eaymond 0. Osbuen. 



The specimen in question is a male of 

 Syrphus arcuatus Fallen (Diptera), a com- 

 mon 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 com- 

 pound eye is entirely wanting. A third an- 

 tenna appears on this side of the head posterior 

 to the normal left antenna and entirely sepa- 

 rated 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 have 

 been suppressed owing to some accident during 

 metamorphosis and that the antenna was pro- 

 duced in place of it. A second vertical tri- 

 angle also appears in this specimen alongside 

 of the normal one. This supernumerary tri- 

 angle is similar to the normal in pilosity and 

 in the arrangement of the ocelli, but the 

 anterior median ocellus has no cornea and is 

 represented merely by a small prominence. 



A fuller description with figures will appear 

 elsewhere. 



Lantern slides were also exhibited showing 

 views of a two-headed turtle with many ab- 

 normalities in the carapace and plastron. 

 A Naturalist in British East Africa: Mr. 



Herbert Lang. 



The Tjader Expedition to British East 

 Africa was undertaken for the purpose of col- 

 lecting material representing the fauna of that 

 region. From Mombasa, the expedition 



