ZOOGENESIS 



Fig. 103.- — The fourth larval stage of a small jellyfish (Glossocodon, 



sp.); see fig. 78, p. 143 . From A. Agassiz. 

 Fig. 104. — A larval stage of an annelid or jointed worm (Leuco- 



dore, sp.). From A. Agassiz. 

 Fig. 105. — The sixth larval stage of a small jellyfish (Glossocodon, 



sp.) ; see fig. 103 . From A. Agassiz. 

 Fig. 106. — A pilidium — a larval form of a nemertean. From A. 



Agassiz. 

 Fig. 107. — A larval stage of a small sea-anemone (Edwardsia, sp.). 



From A. Agassiz. 

 Fig. 108. — A larval stage of one of the annelids or jointed v^^orms 



(Polygordius, sp.). From A. Agassiz. 

 Fig. 109. — A larval stage of the Mediterranean rosy feather-star 



(^Antedonmediterranea)', see fig. 43, p. 87. From A. 



H. Clark, after Bury. 



Early Developmental Stages, and Two Curious Animal 



Types (Page 185) 



Figs. 110-119. — Early developmental stages of a coral (Monoxenia 

 darwinit). FromHaeckel. Figs, iio-iii. — Egg or 

 ovum. Fig. III. — Two celled stage. Fig. 113. — ■ 

 Four celled stage. Fig. 114. — ^The blastula. Fig. 

 115. — The blastula in cross section. Fig. 116. — 

 The gastrula at the commencement of its formation, 

 seen in cross section. Fig. 117. — ^The completed 

 gastrula, seen in cross section, showing the outer 

 (ectodermal) and the inner (endodermal) layers of 

 cells. Fig. 118. — A free-swimming blastula, with 

 cilia. Fig. 119. — A free-swimming gastrula, with 

 cilia. 



Fig. 12.0. — Gastrula of a sea-urchin (Toxopneustes brevispinosus) 

 seen in cross section, showing the mesodermal net- 

 work between the outer (ectodermal) and inner 

 (endodermal) layers of cells. After Selenka. 



Figs. 111-115. — Early developmental stages of a sponge {Sycon 

 ra-phanus). After F. E. Schultze. Fig. iii. — 

 Ovum. Fig. 111. — Four celled stage. Fig. 113. — 

 Sixteen celled stage. Fig. 114. — Blastosphere with 

 large dark granular cells at the open pole. Fig. 



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