60 



NOTE ON THE LARVAE OF GRANTIA 

 COMPRESSA. 



By OLGA M. JORGENSEN. 



At the beginning of September, 1917, specimens of Grantia 

 compressa were obtained containing embryos ready for hatching. 

 The free swimming stages were secured from these both naturally 

 and by the use of the centrifuge, and the folio whig observations 

 made. 



On September 3rd, a few of the sponges were attached to a 

 wire fixed m the mouth of the centrifuge tube, which was then filled 

 with filtered sea-water, and centrifuged for ten minutes. A 

 number of actively swimming amphiblastulae were thus collected. 

 They appeared as shoA\Ti in fig. 1. Next day (nineteen hours 

 later), some of these were still active, but a greater number had 

 ceased to swim about, and the larger granular cells had begun to 

 multiply. A few appeared to be developing normally (fig. 2), 

 but the majority had evidently been affected by the centrifuging 

 and were growing irregularly. These took various forms, some 

 of which are indicated in figs. 3-6. Ten hours later all had ceased 

 to be active. 



On September 5th, all the larvae were dead except two which 

 had settled dowii — the granular cells having overgrown the 

 columnar ones. (Fig. 7.) Two daj^s later they appeared as in 

 fig. 8. They were apparently unchanged next day when they 

 were probably dead, as on September 10th they had disappeared 

 entirely. 



When the first batch of material was centrifuged, a number 

 of other specimens were placed in filtered sea-water and left over- 

 night, when naturally hatched larvae were obtamed. 



Many of these were identical in form with those hatched 

 previously (fig. 1) ,while others showed a decided flattening of 

 the posterior pole (fig. 1a). These larvae were more active than 

 those got by centrifuging — sho"\\dng a quicker forward movement. 



