DESCRIPTION OF PLATES. 



Figs. 13-18 illustrate admirably the variations of the yellow and black 

 in the same species. 



Fig. 13. Ditto, var. Ufarcellus. 



Figs. 1-5 are all one species ; Jevana being the winter form, prorsa the 

 summer form, and porima intermediate. Similiarly 6-7 are the same 

 species, meione being the southern form. So with 8-9 and 11-13, which 

 are only seasonal varieties. Here we can actually trace the way in which 

 varieties are formed. See Weismann's work, cited in the text. 



Plate VI. Syncoryne pulcheUa, magnified. After Professor Allman. Gymno- 

 p. 62. blastic or Tubularian Hydroids. Ray Soc, 1871, pi. vi., figs. 1 



and 3. 

 Fig. 1. A planoblast as seen passively floating in the water after 



liberation. 

 Fig. 2. The entire hydrosoma of syncoryne. 



a. The spadix. 



b. The medusfe or planoblasts in various stages of develop- 



ment. 



