XVI EXPLANATIONS OF THE PLATES. 



PLATE VIII. (p. 244). 

 development of palmogl-ea and PROTOcoccus (after Braun and Cohn). 



Fig. 1, a— i. Successive stages of Binary Subdivision of Palmoghea ; 

 K — M, successive stages of Conjugation. 



2, a — c. Binary subdivision of ' still ' form of Protococcus ; d — g, multi- 

 plication of 'motile' form ; h— l, different phases of 'motile' condition. 



PLATE IX. (p. 252). 



development of volvox globator (after Williamson). 



Fig. 1. Young Volvox; a, primordial cell of secondary sphere ; b. poly- 

 gonal masses of endochrome, separated by hyaline substance. 



2. The same more advanced ; a, a, polygonal masses of endochrome ; 

 b, b, their connecting processes ; c, primordial cell of secondary sphere. 



3. The same more advanced, shewing an increase in the size of the con- 

 necting processes, a, a, and a duplicative subdivision of the primordial 

 cell. 



4. The same more advanced, showing the masses of endochrome more 

 widely separated by the interposition of hyaline substance, and each 

 furnished with a pair of cilia ; whilst the primordial cell, /, has under- 

 gone a second segmentation. 



5. Portion of the spherical wall of a mature Volvox, showing the wide 

 separation of the endochrome-masses still connected by the processes 

 b, b, the lines of areolation, c, dividing the hyaline substance, and the 

 long cilia, e. 



6. 7, 8. Secondary sphere, or macro-gonidium, developed by the pro- 

 gressive segmentation of the primordial cell. 



9. Single cell from the wall of a mature Volvox, showing the endo- 

 chrome-mass, b, to contain two vacuoles, a, a, and to be surrounded by 

 a hyaline envelope, d, having polygonal borders. 



10. Portion of the wall of a young Volvox, seen edgeways, showing 

 that its sphere is still invested by the hyaline envelope of the original 

 cell, which the cilia penetrate but do not pierce. 



11. Two cells from mature Volvox, seen edgeways, showing the enclo- 

 sure of the endochrome-masses in their own hyaline investment, and the 

 persistence of the general investment (here pierced by the cilia) around 

 the entire sphere. 



PLATE X. (p. 300). 



arachnoid iscus japonicus (after E. Beck). 



The specimens, attached to the surface of a Sea-weed, are represented 

 as seen under a l-4th Objective, with Lieberkiihn illumination: — a, in- 

 ternal surface ; b, external surface ; c, front view, showing incipient sub- 

 division. 



PLATE XL (p. 332). 



DEVELOPMENT AND REPRODUCTION OF SPH.EROPLEA ANNULINA (after Cohn). 



Fig. 1. Oo-spore, of a red colour, having its outer membrane furnished 

 with stellate prolongations. 



2, 3, 4. Successive stages of segmentation of the Oo-spore. 



5. Fusiform ciliated Zoospores set free by the rupture of the coats of 

 the Oo-spore. 



