HABITS, ETC., OF CEREBRATaLUS LACTEUS. 133 



About six or eight minutes later the first body returns to a 

 position near the egg, and there awaits the second body. 



A swelling appears at the point where the connecting band 

 of protoplasm from the first body joins the egg (fig. 28). 

 This rapidly becomes nipple- shaped^ lifting the first body 

 upon its slightly enlarged apex (fig. 29). There is the same 

 gradual constriction as before, and the whole formation 

 occupies about the same time, three minutes. There is also 

 a second flattening of the egg, sometimes a slight emargina- 

 tion, whereby the surface is withdrawn from the membranes, 

 so that the combined first and second bodies, even though 

 the latter is elongated, do not get any nearer to them. The 

 second body is smaller than the first, and does not become 

 spherical, but is elongated parallel to the surface of the egg 

 into a spindle or melon shape (fig. 35). 



Sometimes the first body divides after separation, or, in- 

 stead of a single second body, two occasionally appear side 

 by side. 



In both these abnormal cases one of the paired bodies 

 withdraws by itself, while the other two remain and continue 

 their filose activities. 



Activities of the Polar Bodies. — During their for- 

 mation and almost to the blastula stage the polar bodies 

 afford a remarkable example of that form of protoplasmic 

 activity which was first described in echinoderm eggs by G. 

 F. Andrews, and designated '' filose activities or spinning " 



(4). 



These activities have already been carefully described 

 in this Nemertean in an interesting paper by Dr. E. A. 

 Andrews (2), in which some doubt was expressed as to the 

 certainty that such activities were entirely normal. The 

 eggs used by Dr. Andrews were fertilised artificially, but 

 great care was used in observing them, and the results were 

 verified by comparison with other eggs which developed into 

 normal embryos. I am glad to add in confirmation the 

 following description taken from eggs laid in an aquarium 

 under fairly normal conditions and fertilised naturally. 



