406 BULLETIN OF THE 



presents the same appearance as the button used to upholster a cushion. 

 After a short time the button disappears, and in its place there remains 

 a hole such as arises in making a thrust into a doughy mass. This hole 



— there may be several of them — may remain till segmentation ensues, 

 or it may disappear earlier. The yellow spot ultimately vanishes. 



Is not this " button " identical with the spheroidal structures discov- 

 ered in fishes by Oellacher, and considered by him as the representatives 

 of the polar globules 1 



Of the results attained by Butschli ('75", p. 430) in a second prelimi- 

 nary paper, I will here call attention only to the modification of his views 

 concerning the source of the spindle-shaped body. He now believes it 

 must be considered the metamorphosed nucleus rather than nucleolus, 

 and that in the light of this his previous conclusions are to be correspond- 

 ingly modified. Further details of his paper are given at page 289. 



Selenka ('75, p. 444) compresses into few words his observations on 

 Phascolosoma elongatum. Some time after fecundation the germinative 

 vesicle disappears, the yolk contracts, and there is pressed out a drop of 

 protoplasm, which he thinks may be the remnant of the "cell nucleus," 



— perhaps excrement of the egg. I think it is without doubt a polar 

 globule. 



Fol's ('75«, pp. 104-108, 198, PI. I. Figs. 3, 4, PI. VII. Fig. 2, and 

 PI. VIII. Figs. 1-3) illustrated paper on the development of Pteropoda, 

 beside giving a summation of results (p. 198) in the words of his prelimi- 

 nary paper, furnishes additional facts of interest, and affords by the fig- 

 ures a better means of judging accurately the nature of his observations. 



He says the centre of the delicate star which occupies the middle of 

 the formative part of the egg at the time the latter is laid, is not occu- 

 pied, as one might expect, by a corpuscle differing from the surrounding 

 stroma ; the granules composing the star also occupy its centre. No 

 activity is to be attributed to the granules themselves ; they are only the 

 landmarks, as it were, of the intimate molecular movements of the proto- 

 plasm which one is unable to observe directly. Some minutes after the 

 egg is laid this star begins to elongate in the direction of the long axis of 

 the egg. It soon divides into two stars, of which one continues to occupy 

 the centre of the protoplasm, while the other reaches the surface in the 

 middle of the protoplasmic area. This point then becomes elevated as 

 a small nipple, and separates itself from the yolk as a spherical globule, 

 for which Fol adopts the term corpuscle excrete, or corpuscle de rebut, 

 as better reflecting than does the term " Richtungsblaschen " its entire 

 want of significance in the subsequent development. This polar globule 



