Section I. 

 Description of the species. 



Subtribus Protactininae. 



Family Gonactiniidae. 



Diagnosis: Protactininae with flattened, disclike, proximal body-end. Column of the same struc- 

 ture as the tentacles with spirocysts and a more or less strongly developed, longitudinal muscle- and nerve- 

 layer, not capable of involution. No distinct sphincter. Longitudinal muscles of the tentacles ectodermal 

 (in Gonactinia sometimes with a little tendency to be meso-ectodermal?) even as the radial muscles 

 of the oral disc. Actinopharynx not rudimentary, with longitudinal muscles and often with spirocysts, 

 with weak siphonoglyphes or without. Mesenteries typically arranged in cycles, each pair of mesenteries, 

 except the directives, with the longitudinal muscles facing each other. 8 (the " Edwardsia-mesenteries") , 

 10 or 12 mesenteries perfect. Reproductive organs arranged in the usual manner, as a rule on all perfect 

 mesenteries. Muscles of the ' mesenteries weak, especially the parieto-basilar muscles. No ciliated lobes to 

 the mesenterial filaments. Stomata absent or only the oral stomata present. 



In this family I have previously (1900) placed the genera Protanthea, Gonactinia and preliminarily 

 also Boloceroides. Concerning the last genus, which has formerly been referred to the Boloceriidae, its affi- 

 nity with Protanthea and Gonactinia has been admitted by Pax (1914 p. 608) and Poche (1914 p. 97), 

 whereas Me. Murrich (1904 p. 255) and later Stephenson (1918 p. 6) have not accepted it as belonging 

 to the family Gonactiniidae. These latter authors, however, have not given any important arguments for 

 their point of view, no more have they refuted my objections against the affinity of the genus with the Bolo- 

 ceriidae (vide Carlgren 1911). As I have pointed out, one of the differences between Protanthea and Go- 

 nactinia on one side and Boloceroides on the other is that the former are devoid of ciliated streaks on the 

 filaments, the latter not. In 1900 I also proposed to establish a special subfamily for the genus Boloceroides. 

 Though I am continually of opinion that Boloceroides is nearly related to the above-mentioned species, I 

 think that it may be the most practical to refer it with Bunodeopsis and Alicia to the family Aliciidae, a 

 heterogeneous family, as I will show in another paper. 



To the family Gonactiniidae I furthermore refer the genus Sideractis. The diagnoses of this family 

 and of the genera Protanthea and Gonactinia are a little altered and more detailed here. 



The Ingolf-Expeditioii. V. g. 1 



