THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY, 



[FOURTH SERIES.] 



" per litora spargite moscum, 



Naiades, et circiim vitreos considit* fontes: 

 Pollice virgineo teneros hie far])ite florea : 

 Floribus et pictum, divee. replete canistrum. 

 At voB, o Nj-mphae Craterides, ite sub undas: 

 Ite, recurvato variata corallia truneo 

 Vellite muscosia e rupibue, et mihi conchas 

 Ferte, Deje pelagi, et pineui conchylia suoco." 



N. Parthenii Giannettatii Eel. 1. 



No. 85. JANUARY 1875. 



I. — Observations on HdcheVs Gastr^ea Theory. 

 By Dr. W. Salensky*. 



[Plate v.] 



Hackel's investigations on the Calcispongige, wliich are 

 brought together in his admirable monograph, have led him 

 to a theory to which he ascribes great importance for the con- 

 ception of the phylogenetic relations of the types of animals, 

 and which he calls the Gastrcea theory. This theory was first 

 presented in its chief features in the portion of the raonogra])h 

 treating of developmental history ; but Hiickel has since pub- 

 lished a special memoir upon it and expounded it much more 

 in detail and with relation to the germ-lamella theory f. 



In its principal features this theory may be summed up 

 very shortly. It consists chiefly in the statement that in the 

 ontogenetic development of all the representatives of the vari- 



♦ Translated by W. S. Dallas, F.L.S., from the 'Archiv fur Natur- 

 geschichte,' 1874, pp. 1.37-174. 



t Hiickel, ' Die Gastroea-Theorie, die phylogenetische Classification und 

 die Homologie der Keirablatter.' 



Ann. t& Mag. N. Hist. Ser. 4. Vol.xv. 1 



