278 WILSON. [Vol. IX. 



Page 



II. Adult Structure and Gemmule Development of Tedania 

 Brucei, n. sp. 



1. Adult 320 



Collecting and Embryological Methods 325 



2. Development of the Swimming Larva 327 



Formation of gemniules 327 



Development of gemmule into swimming larva 329 



Structure of the swimming larva 331 



3. Metamorphosis 332 



Attachment 332 



Ectodermal membrane and peripheral mesodermic zone 335 



Canal system 337 



III. Adult Structure and Egg Development of Tedanione 



foetida, n. g. 



1. Adult 338 



2. Development 341 



IV. Early Stages in Egg Development of Hircinia acuta 346 



V. Remarks on the Morphology of Sponges 348 



Evidence from comparative anatomy as to sponge phylogeny 350 



Embryological evidence as to sponge phylogeny 357 



Origin of the Olynthus 362 



VI. Remarks on the Gemmule Development of Sponges. 



1. Asexual Development in General of the Sponges 364 



2. Comparison between the Egg Larva and Gemmule 



Larva of Silicious Sponges 368 



Resemblance between the two kinds of larvae 368 



Cause of the resemblance 370 



The observations described in the present paper were begun 

 more than four years ago, when as Bruce Fellow of the Johns 

 Hopkins University I was permitted by the directors of the 

 fellowship to spend a considerable part of the academic year in 

 the Bahama islands. For their kindness in complying with my 

 wishes in this matter I thank them heartily, and trust they may 

 find in the following pages some justification of that pleasant 

 excursion. 



The investigation has been subject to many interruptions. 

 On returning from the Bahamas it was prosecuted for a time 

 in Professor Brooks's laboratory, but other duties incident to 

 my connection with the U.S. Fish Commission interfering, it 

 was laid aside until midsummer, 1890. The Commissioner, 

 Hon. Marshall McDonald, feeling that any enlightened attempts 



