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THE AMERICAN MUSEUM JOURNAL 



stages by vertical divisions, at the end of which time it appears 

 as a circular disc divided into eight equal segments. These 

 again divide into a 32-celled stage by means of a horizontal or 

 equatorial cleavage, and then, by repeated divisions of the eight 

 upper cells, a hollow sphere is formed composed of eight large 

 granular cells and many small cells, each of the latter bearing a 

 long flagellum or whip-like filament. The eight large cells 

 divide more slowly, always remaining comparatively large, and 

 are not provided with flagella. 



At this so-called blastnla stage the larva issues from the 



FIG. 16.— A GROUP OF NEPTUNE'S GOBLET SPONGES ^Potcrion «</;■««*•/ Hartlng.) 

 The tallest specimen is 33 inches high. 



endoderm of the parent and finally passes out through the osculum 

 of the sponge. It swims rapidly about with its flagellate portion 

 in front, and after a time the large granular cells grow aroimd and 

 enclose the flagellate cells. Soon a sup-chaped body is formed, 

 known as the gastrula, which is covered with non-flagellate 

 cells, and lined with a multitude of flagellate cells. The opening 

 of the cup, or blastopore, now narrows and almost immediately the 

 larva settles down and becomes fixed by the rim of the blastopore 

 to a rock or some other object. The development is now very 



