420 Royal Society :— 



without exception. In older specimens one or more cells are 

 lost, and the frond becomes therefore apparently irregular 

 {I c. 26). 



1. Pandorina (Pritchard, Dlat. pp. 157, 517, 1. 19. f. 59-69) and 



Eudorina are the same. 



2. Gonium. (Pritchard, Diat. pp. 152, 517, t. 19. f. 32-37.) 



3. Volvox. (Pritchard, Diat. pp. 180, 526, t. 20. f. 32-47.) 



4. StepJianospharia. (Pritchard, Diat. p. 529, t. 19. f. 38-58.) 



According to Dr. Hicks, i\\& , Volvox is perpetuated in two 

 ways : 1, by the encysted cell or oospore ; 2, by the motionless 

 segment of the zoospore, which clearly has its homologue in 

 many Algse, and is free from motion because without cilia, and 

 thereby distinguished from zoospores. (Quart. Journ. Microscop. 

 Science, 1861, p. 283, t. 9. f. 1-11.) 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



^ June 20, 1861. — Major-General Sabine, Treasurer and Vice-Pre- 

 sident, in the Chair. 



"On the Anatomy and Physiology of the Spongiadse" (Part II.), 

 by J. S. Bowerbank,' LL.D., F.R.S., F.L.S., &c. 



This paper is a continuation of the first division of the subject, 

 published in the Phil. Trans, for 1858. 



In the second part of this division the author treats of the kera- 

 tode or horny substance of the skeleton, as regards both its physical 

 and chemical charactei*s, with a view of establishing the animal na- 

 ture of that substance. 



In the third part the membranous tissues are described under 

 two heads : — 



1st. Simple membranous tissues analogous to those of the base- 

 ment membranes of the higher classes of animals ; and 



2nd. Compound membranous tissues. These structures consist 

 of simple membranous tissue combined with primitive fibrous tissue. 

 Their most simple forms exist in the membranes lining the intersti- 

 tial cavities of the sponge and in the dermal membrane. 



In the fouith part the fibrous tissues are described as consisting 

 of three principal divisions. 



1st. Primitive fibrous tissue. These structures are exceedingly 

 minute, and form an important element in the construction of the 

 compound membranous tissues of the animal. 



2nd division. The fibres of the skeleton are described under the 

 following heads : — 



1st. Solid simple keratose fibre. 



