Activities of Polar Bodies. 1 1 5 



CerehratuJus, there is no doubt that there were here also 

 radiating branches of processes similar to those so common at 

 the ends of the second polar body of Cerehratulus. The first 

 polar body also showed very fine Helioza-like radiations in 

 one case. One polar body showed marked amoeboid change 

 of outline, with a rounded blunt pseudopodiura. 



Such amoeboid changes of polar bodies are most pronounced 

 in another lamellibranch, Angulus tener. As represented in 

 figure 5, the larger, first polar body takes on a somewhat 

 cylindrical shape at a time when the second is rounded and 

 not entirely free from the Qgg, and sends out blunt pseudo- 

 podia, the two bodies remaining closely appressed. Besides 



Fig. 5. 



the rounded pseudopodia, which are represented as dark, 

 there were also clear delicate lateral sheets or lamellse of wavy 

 protoplasm, which are indicated in outline. All these parts 

 rapidly changed, as may be seen by comparing the left-hand 

 view with the right, an interval of scarcely a minute having 

 passed between these two sketches of the same polar body. 

 As these observations were made with the 6 ocular and 

 2 millim. objective, the failure to see spin-threads here does 

 not disprove their existence ; in one case there seemed to be 

 something connecting the first polar body with the Qgg and 

 passing like a filament between them ; but the general cha- 

 racter of these polar bodies was that of amoebee, and not that 

 of filose rhizopods. 



To sum up : we find that the polar bodies in certain 

 representatives of the groups — Echinodermata, Mollusca, and 

 Nemertini — show marked activities, differing in different 

 groups and in different subgroups. In several groups the 

 polar bodies have not only amoeboid but strongly marked 

 Heliozoan activities. The polar bodies in several groups 

 remain vitally connected with one another and with the 

 developing embryo for some time after their extrusion. 



