82 SYNOPTIC COLLECTION. 



of development of another species, Chalinula fertilis 

 Keller, and by so doing has thrown strong light on many 

 important points. Besides the asexual mode of increase 

 through budding, there occurs a sexual propagation, the 

 latter probably taking place only in the spring. In this 

 sponge the sexes are distinct, the females being two or 

 three times larger than the males. As soon as the forma- 

 tion of the egg begins the ordinary brown color of the 

 female changes to red, becoming in very vigorous animals 

 almost a cherry red. This color disappears after fertili- 

 zation or at the beginning of the egg furrowing, and the 

 female becomes ochre yellow at the time the larvae 

 swarm out. The males do not change their color. PL 

 84, fig. i, is a young, unfertilized egg which possesses 

 amoeboid movements. Fig. 2 represents a spermatozoon 

 which reminds one of a flagellate Protozoan. Fig. 3 is a 

 mature egg which has become spherical in form and sur- 

 rounded by a capsule. Nutritive mesoderm cells are seen 

 near it. The capsule is formed early and it must be 

 assumed, therefore, that the spermatozoon pierces it in 

 order to reach the egg within. After impregnation, the 

 furrowing takes place quickly, and normally covers from 

 twenty to thirty hours. It is total, but the cells are un- 

 equal in size and there is no segmentation cavity. Fig. 

 4 shows the first two furrowing cells ; fig. 5, the stage 

 with four cells lying in a plane. In fig. 6 (figs. 6-9 drawn 

 without capsule) these cells have arranged themselves in 

 a pyramidal form, the large cell being the parent cell of 

 the endoderm. Fig. 7 has seven cells and fig. 8 fourteen . 

 cells. Here the two large endoderm cells are partly 

 surrounded by ectoderm cells. In fig. 9 the endoderm 

 forms a central mass of cells and appears at the peri- 

 phery as a plug. The other cells on the surface are ecto- 

 dermic. 1 



1 According to Wilson (see " Notes on the Development of some 

 Sponges," Journ. of Morphology, V., no. 3, 1891, p. 516), it is 

 probably not the endoderm that protrudes at this pole, but the 

 ectoderm, which is greatly flattened over this region. 



