258 C. O. WHITMAN. 



O. Hertwig (^1) was the first to prove that they are the morpho- 

 logical equivalents of cells} 



In regard to their physiological signification, little or nothing 

 is known, Friedrich Miiller ('t') t^upposed that the direction 

 of the cle.ivage was determined by the influence of these cor- 

 ])u.«cles, and therefore named them " versiculae directrices}' 

 That they play no such important role in the developement of 

 the egg, is now generally admitted. That thij have no such 

 function appears evident from the fact that in eggs which have no 

 membrane they escape into the surrounding fluid. The fact that 

 the polar globules have no known morphological or physiological 

 relation with the future embryo, has led some authors to interpret 

 them as refuse material, which is thrown oft' as excrement ("Koth 

 des Eies," Selenka, 44^, \\\', '' Corpuscule excrete," J^'ol.-j\V)^ 

 or ejected by way of defecation (Semper 'aV)- '^'^^''t no such in- 

 terpretation is admissible has already been clearly shown by 

 Biitschli (-rVir)- 



The question as to the historic origin of the polar corpuscles 

 is undoubtedly one of considerable interest, and has already 

 begun to engage the attention of investigators. Owing to the 

 fact that we are but just beginning to see what really takes place 

 during the process of fecundation, few naturalists have ventured 

 to approach this question from a phylogenetic standpoint. 

 Theories however have their value even when based on few and 

 imperfectly understood facts ; for we never approach the truth 

 more rapidly than when we are *' hunting down " a theory. 

 Rabl, who was the first to attack this problem, assigns to the polar 

 globules a cenogenetic origin. These " elastic balls,^^ he says 

 (i-QTj afy)* ^^"6 " nothing (jiit protective organs (f the emfjri/o, 

 acquired in adaptation to unequal cleavage.'^ This theory, 

 ingenious as it may be, seems to have no basis whatever in fact. 

 There is not the sliglitest evidence that the embryonic cells arc 

 protected by these globules, nor is there any evidence that they 

 need protection against a ])rotective envelope. The egg of 

 Clepsine furnishes a good example of unequal cleavage and is a 

 fair case for studying the point in question. 



The formation of the first embryonic cells shows plainly that 

 they are not easily injured by pressure. The first cell is nearly 

 round at the completion of its formation, but, while the second 

 cell is forming, is pushed out of its original place and so pressed 

 into one of the large cleavage-spheres, that it is dilHcult for a 

 time to recognise its outline. Shortly after the production of 



• Brandt (oVt) recognised the cell-cliaractcr of the polar globules, but 

 thinking tliat they were wholly derived from the irenninal vesicle, was eoni- 

 pelled to reiiiird this vesicU; as a cell. This view of the germinal vesicle is 

 also eiitertaiacd by BischuH" (j!;,') and Villol {\Vl)- 



