432 BULLETIN OF THE 



The least intelligible part of the observations on Cucullanus is the total 

 ejection of the spindle in an undivided state, and its resting intact on the 

 surface of the yolk. This is less likely to be a normal condition of affairs 

 from the fact that stages in the formation of the polar globule quite like 

 those observed in other animals were seen and figured by Biitschli. 



Observations on several non-parasitic nematodes contribute nothing of 

 special interest concerning the formation of the polar globules, but con- 

 firm the existence of two pronuclei which ultimately become fused. 



The observations on Lymnaeus and Succinea confirm the conclusions 

 reached with Nephelis. The earliest eggs studied exhibit a flattened 

 yolk ; one of the poles of the axis thus determined is characterized by a 

 low, broad, conical elevation of clear protoplasm. In the short axis lie 

 two " areas " and their suns, one near the centre, the other nearer the 

 elevated pole, and between the two stretch curved fibres (spindle body). 

 Zones of thickenings do not seem to have been observed till the polar 

 globule was already formed, at least none are figured. This spindle figure 

 migrates toward the surface till one of the "areas " comes to lie in the 

 surface of the elevated portion of the yolk. This area does not seem to 

 have exhibited any central flattened corpuscle such as Limax shows ; but 

 aside from this and the absence of lateral zones the stage represented in 

 Fig. 2, Taf. IV. of Biitschli's w^ork corresponds very closely with Fig. 50 

 of Limax. The polar globule is produced as in Nephelis, but the author 

 thinks he has seen the already formed second globule lying still within 

 the yolk, and joined to the globule already ejected by a slender pedicel, 

 — an observation that one cannot now expect to see confirmed. There 

 is some confusion in his mind regarding the persistence of these two sys- 

 tems of rays, apparently resulting from an incomplete conception of the 

 relation of the polar globules to the spindle. The protoplasm found at 

 this pole immediately after the ejection of the first polar globule is lim- 

 ited by a sharp but feebly expressed boundary from the granular proto- 

 plasm of the yolk. I have never seen it so sharply defined as he portrays 

 it in his Figs. 3, 5, and 17, Taf. IV. It was this feature which helped 

 to mislead the author into the earlier belief that a remnant of the ger- 

 minative vesicle remained behind in a recognizable form. 



As to the formation of a new nucleus Biitschli says that close under 

 the surface where the polar globules are formed there appear in Lymnaeus 

 a number (nine or more) of small nuclei close together. Each possesses 

 a distinct dark membrane, and, within the clear fluid contents, a few dark 

 CLorpuscles with clear centres. The latter adhere closely to the mem- 

 brane. These nuclei melt together, so that at a later stage, although 



