EXPLANATION OF PLATE VIL 



Fig. 31. — Archigastrula of the same Snail. Alter Carl Rabl (Ibid,, 

 Taf. vii, fig. 11). 



Fig. 32. — Ampbipastrula of a Snail (Purpura). After Selenka (' Keim- 

 blatter bei Purpura," ' Niederl. Archiv f. Zool./ 1871, Heft ii, Taf. xvii). 



Fig. 33. — Archigastrula of a Sea-star (Asteracanthion). After Alexander 

 Agassiz (' Embryology of the Star-fish,' 1864, Plate i, fig. 27). 



Fig. 34. — Amphimorula of a Rhizocephalon (Sacculina). After Ed. 

 Van Benedeu (' Recherches sur rEmbryologie des Crustacees,' 1870, Plate 

 i, fig. 21). 



Fig. 35. — Discomorula of a Slater (Oniscus). After Bobretzky (" Zur 

 Embryologie des Oniscus murarius,'' ' Zeitschr. fur Wissensch. Zoologie,* 

 Vol. xxiv, Taf. xxi, fig. 3). 



Fig. 36. — Discoblastula of the same Oniscus. After Bobretzky (Ibid., 

 fig. 5). 



Fig. 37. — Discogastrula of the same Oniscus. After Bobretzky (Ibid., 

 fig. 7). 



Fig. 38. — Discogastrula' of a Water-beetle (Hydrophibus). After 

 Kowalewsky (' Embryologie Studien an Wurmen und Arthropoden,' Peters- 

 burg, 1871, Taf. ix, fig. 23). 



Fig. 39. — Archigastrula of a Pteromaline (Platygaster). After Ganin 

 (" Entwick. der Insecten," ' Zeitschr. f. Wiss. Zoologie,' 1869, Bd. xix, 

 Taf. xxx). 



Fig. 40. — Discogastrula of the Scorpion. After Metschnikoff (" Embryol. 

 des Scorpinons," * Zeitschr. f. Wiss. Zool.,' 1871, Taf. xiv, fig. 9). 



PLATE VIII. 



In all the figures the Entoderm is marked red, the Exoderm blue. The 

 food-yelk is mostly coloured red. s, Cleavage-cavity (blastocoel) ; a, cavity 

 of the primitive enteron ; o, blastopore (Urmuud of Haeckel). 



Fig. 41. — Archiblastula of the Amphioxus. After Kowalewsky (" Ent- 

 wick. des Amphioxus," ' Mem. Petersburg Akad.,' 1867, Vol. xi, Taf. i, 



fig- 9). 



Fig. 42. — Archiblastula invaginata of the Amphioxus. After Kowalewsky 



(Ibid., fig. 13). 



Fig. 43. — Archigastrula of the Amphioxus at its commencement. After 

 Kowalewsky (Ibid., fig. 14). 



Fig. 44. — Archigastrula of the Amphioxus completed. After Kowalewsky 

 (Ibid., fig. 16). 



Fig. 45. — Amphimorula of Petromyzon. After Max Schultze ('Ent- 

 wick. von Petromyzon,' Haarlem, 1856, Taf. iv, fig. 1). 



Fig. 46. — Amphiblastula of Petromyzon. After Max Schultze (Ibid., 

 fig. 2). 



Fig. 47. — Amphigastrula of Petromyzon at its commencement. After 

 Schultze (Ibid., fig. 5). 



Fig. 48.^Amphigastrula of Petromyzon, complete. After Schultze 

 (Ibid., fig. 7). 



' It has not been my intention to criticise all the interpretations 

 which Haeckel has offered of developmental forms in the present notice, 

 but I must express my difficulty in interpreting the ontogeny of Hydrophilus 

 as belonging to the Discoblastic type. It seems to me rather to be a 

 very much modified Periblastic form. — E. R. L. 



