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THE AMEBIC AN NATURALIST [Vol. LV 



the end of the egg-belt. This abnormality was much 

 greater in the second nidosome, in that there was a much 

 greater number of small capsules with only one or a few 

 eggs in them. There were also capsules actually without 

 eggs. Some eggs failed to develop; some gave off the 

 polar bodies and then did not advance any farther; others 

 did not form polar bodies. It was of great interest, in- 

 deed, to watch the development of the embryos in the 

 large capsules which in some cases contained more than 

 twenty eggs (Fig. 7). Within a few hours, there would 

 be twice or even three times as many polar bodies as eggs 

 (of course within the capsules), because the first polar 

 body sometimes divided. A detailed study of the blasto- 

 meres was not undertaken. Figures 4 to 6 show a few 

 early developmental stages, and early and late larval 

 stages are showm in Figs. 7 and 9. An embr\'Onic shell 

 is shown in Fig. 10 ; veliger larvae in Fig. 9. 



When the embryos reached the gastrula stage they 

 swam about within the capsules. On the fifth day after 

 being laid the whole egg-body was practically alive with 

 imprisoned swimming larvae (Fig. 9). Nine days later, 

 the larvae began to leave the capsules. It was surprising 

 to see h6w rapidly the embryos advanced from day to 

 day, going through the trochophore and veliger stages. 

 During the latter stage the shell was very prominent ; it 

 resembled the shell of Natica russa, in that it had a blunt 

 apex and short body; the posterior or tapering part of 

 the shell had no spiral turns; the posterior edge of the 

 aperture had a small indent; the edge of the aperture' 

 of the shell was otherwise without any modifications 

 (Fig. 10). The animal itself did not assume the adult 

 shape before it lost the shell, but when it left tlif c'a])sule 

 it shed the shell, and the young began the Wiv of a 

 so-called naked mollusk. The ])resenc(' of a shell witli 

 operculum in embryonic life of Xudibiaiiclis ha- lucii ol)- 

 served by various authors: Alder and I lancdck. 1^4:); 

 Pelseneer, 1893;Smith, Bell and Kirlq.at liek. VMU; r>(.a>. 

 1916, and others. 



