66 PROFESSOR E. RAY LANKESTER. 



Summary of the facts known as to Gastrula- formation in 

 Zoological order} 



SpongIjE. Arclublasl ic, ampliiblastic. 



Hybkomedus.e. Archiblastic (Cassiopeia, Rhizostoma, Pelagia, Kowalew- 



ski/). Delamlnate, probably disguised archiblastic and ampliiblastic 



(Hydroid polyps). Ampliiblastic (many Siplionophora, Haeckel). 



Discoblastic (pertiaps some Siplionophora). 

 Ctenophoka. Ampliiblastic (many or all. Kowalewsliy , Fol, Agassiz) 



possibly some discoblastic (llaeckel). 

 AcTiNOZOA. Archiblastic (Actinia, Caryophyllia, Gorgonia, and Cereanthus, 



Kowalewski/, Monoxenia, Haeckel). Periblastic (Alcyonians, Kowa- 



leicski/). Deiaminate, perhaps disguised archiblastic (some species 



of Actinia, Kowalewski/). 

 Vermes. Archiblastic (Neniertines, Metsclinikoff, Bieck. Balanoglossus, 



Sagitta, Kowaleicsky . CucuUanus, Butschli. Phoronis, Kotcalewski/). 

 Amphiblastic (various epibolic and entobolic varieties among Platy- 



elminthes, Nematoda, and Annelida, described by Leuckari, Cla- 



parede, Kowalewski/, &c., among Rotifera by Sulensky, in the 



Gephyrean Phascolosoma by Seleiika). 

 Discoblastic (not known, but Euaxes furnishes a transition from 



amphiblastic to this type, Kowalewski/). 

 Periblastic, not known. 

 MoLLTJSCA. Archiblastic (Argiope, Terebratula, Kowalewsky. Pisidium, 



Lankesier). 

 Amphiblastic (Thecidium, Kowalewsky, Unio, Rabl, Limnseus, lan- 



kester (not archiblastic), Purpura, Selenka, Trochus, llaeckel, 



Aplysia, Neritina, Lankester, Pterpods, Fol). 

 Discoblastic (Cephalopods, Kblliker). 

 EcHiKODEiiMA, Archiblastic (Holothurida, Kowalewsky, Asterida, Agassiz, 



Echinida, Haeckel, Crinoida, Wyv. Thomson). 

 Amphiblastic (Uraster MuUeri, Echiuaster Sarsii, Pteraster niilitaris, 



Amphiura squamata, and other viviparous Asterida, Anochanus 



chiuensis and allied Echinida, Thelenota tremula, Phyllophorus urna, 



Synaptula vivipara, Cucumaria doliolum among Holothurida). 

 Discoblastic and Periblastic type not known. 

 Aktukopoda. Archibliistic (some Biauchiopoda and Copepoda, Van Bene- 



den, Tardigrada, Katifmaiuiy the Pteromalina, Ganiti). 

 Amphiblastic (some lower Crustacea, Van Benedev, and Bessels, some 



lower Tracheata). 

 Discoblastic (some larger forms of Crustacea, Van Beneden and Bessels, 



Oniscus, Bobretzky, Scorpio (fig. 40), Melschnikoff). 

 Periblastic (most Crustacea, Limulus, Fackard, most Myriapods, 



Arachuida and Insects, according to observations of Bobretzky, Van 



Beneden and Bessels, Weismann, Kowalewsky, Claparede, and Meisch- 



niknff). 

 Vebtebkata. Archiblastic (some Ascidians, Kowalewsky, Amphioxus, 



Kowalewsky). 

 Amphiblastic (some Ascidians, Kotcaleicnky, Cyclostoma, Schullze, 



Amphibia, Ganoids, Owsjanmikow, Marsupials?, Placentals). 

 Discoblastic (Pyrosoma, Huxley, Kowalewsky, Selachians, Balfour, 



Teleosteans, Birds, and Monotrema ?) 

 Periblastic. This type has not been recognised in any Vertebrata. 



1 This list and its zoological arrangement is modified and extended from 

 the references given by Haeckel. 



