388 APPENDIX, 



splendid Venus' girdle of tlie Mediterranean (Cestnm), the colours 

 of wMcli are as varied as those of the rainbow. The actual body 

 of the animal, which lies in the centre of the long belt, is very- 

 small, and constructed exactly like that of the melon-jelly 

 (Cydippe), which floats above to the left (16). On the latter are 

 visible the eight characteristic fringed bands, or ciliated combs, 

 of the ctenophora, and also two long tentacles which extend right 

 across the page, and are fringed with still finer threads. 



Plates YIII. and IX. (Between pages 170 and 171, Vol. II.) 



History of the Development of Star-fishes (Echinoderma, or 

 Estrella). The two plates exhibit their alternation of generation 

 (vol. ii. p. 168), with an example from each of the four classes of 

 Star-fishes. The sea-stars (Asterida) are represented by Uraster 

 (J.), the sea-Hlies (Crinoida) by Comatula (B), the sea-urchins 

 (Echinida) by Echinus (0), and finally, the sea-cucumbers 

 (Holothurise) by Synapta (D). (Compare vol. ii. pp. 166 and 176). 

 The successive stages of development are marked by the numbers i 

 1-6. 



Plate VIII. represents the individual development of the first 

 and non-sexual generation of Star-fishes, that is, of the nurses 

 (usually, but erroneously, called larvae). These nurses possess 

 the form- value of a simple, unsegmented worm-individual. Pig 1 

 represents the egg of the four Star-fishes'; and it, in all essential 

 points, agrees with that of man and of other animals. (Compare 

 vol. i. p. 297, Fig. 5.) As in man, the protoplasm of the egg- 

 cell (the yolk) is surrounded by a thick, structureless membrane 

 (zona pellucida), and contains a globular, cell-kernel (nucleus), 

 as clear as glass, which again encloses a nucleolus. Out of the 

 fertilised egg of the Star-fish (Fig. A 1) there develops in the 

 first place, by the repeated sub-division of cells, a globular mass 

 of homogeneous cells (Fig. 6, vol. i. p. 299), and this changes into 

 a very simple nurse, which has almost the same shape as a 

 wooden shoe (Fig. A 2 — D 2). The edge of the opening of the 

 shoe is bordered by a fringe of cilia, the ciliary movements of 



