29 



globe. Viewed under a higher power of the microscope, the green 

 spots at the meeting of the lines are found to be clusters of deli- 

 cate hair, and doubtless it is owing to their action that the Volvox 

 constantly rolls through the water. For a long time the Volvox 

 was considered a low form of animal life, and was classed under 

 the Infusoria, but is now grouped with the Algae. Though en- 

 dowed with the peculiar motion alluded to, there is no reason 

 why it should be called an animal on that account, since zoospores 

 with movable cilia are not at all uncommon among undoubted 

 plants. Finally, the old Volvox breaks up, the young ones escape 

 from their temporary prison, and, floating away on their own ac- 

 count, grow to the size of their parent, and enclose little rolling 

 balls within themselves as did their progenitors. 



SEPTEMBER. 



Mr. Sibert Saunders, of Whitstable, read a paper in con- 

 tinuation of his former interesting account of the Cirripedia. 

 His special object on this occasion was to show the structure of 

 the shell of the stalkless barnacle, and its mode of growth. This 

 he did by means of descriptions, illustrative diagrams, and 

 specimens prepared to show the component parts of the shell. 



To a casual observer it is not easy to understand how so 

 apparently fixed and solid a shell as that of the stalkless barnacle 

 is enlarged with the growth of the animal. Mr. Saunders showed 

 how beautifully intricate, how exquisitely perfect, are the means 

 provided for this purpose. The shell which appears to consist of 

 a single piece, of irregular external shape, is really a compound 

 structure, consisting of 4, 6 or 8 compartments. These com- 

 partments are invariably arranged in a definite order ; the one 

 fitting into and interlocking with the others on either side of it 

 by means of sutures, and by extensions of the sides, termed, 

 according to their shape and position, radii or alee. Nor is the 

 shell itself in most genera solid throughout ; on the contrary its 

 external and internal laminae are united by a beautiful system of 

 connecting septa. The upper portion of the shell is strengthened 

 by an internal hoop' called the sheath, formed by a thickening of 

 a portion of the inside surface of those compartments which 

 overlap the alee so as to form a ridge into which the edges of the 

 alae are received. 



The basis of the shell in some species is composed of mem- 

 brane ; in others it is calcareous, and sometimes consists of two 

 laminae separated by septa, in the same manner as the walls. 

 The basis is cemented to whatever surface the animal first be- 

 comes attached. By additions to the basis round the circum- 

 ference, and to the compartments on the edges of the radii and 



