REPORT ON ACTIXIARIA. 



229 



arrangement of the large and small mesenteries. I cannot 

 make any statement as to the arrangement of the reproduc- 

 tive organs since only a few scattered ova were to be found in 

 the specimens examined. The mesogloeal ridges of the sto- 

 matoda?um in the present specimens were much stouter than 

 in the Fish Commission examples, though of the same general 

 form. There were from twelve to fourteen of these ridges 

 in the Station 29 specimens and about twenty in the large speci- 

 men from Station 64. Only one siphonoglyph was well marked, 

 although there were two pairs of directives. 



The structural differences between the West Indian speci- 

 mens and those collected by the Fish Commission are but 

 small and do not seem to warrant the establishment of a new 

 species. They are in all probability referable partly to the 

 method of preservation and partly to age. 



A word may possibly be in order as to the suggestion of 

 Carlgren ('93) that this form should be referred to his order 

 Protantheas. I must dissent from such an arrangement, as I do 

 not think that the order can stand, based as it is solely on the 

 occurrence of an ectodermal musculature in the column wall. 

 It is true that this characteristic may be regarded in one sense 

 as primitive, but it is a long journey back from the Hexactiniae 

 to the Scyphistoma to find the origin of it. It seems to me 

 much more probably a sporadic resurrection of an ancestral 

 characteristic and that it has little phylogenetic significance. 

 The acceptance of it as of classificatory importance will lead to 

 the association of forms which in other respects appear to 

 have widely different affinities, e.g., Gonactinia with Coral- 

 limorphus (?) and the form described by Hertwig ('88) as 

 Corynactis sp.? I believe the development of the mesenteries 

 to be a much more reliable phylogenetic character and I see 

 no reason for the obliteration of the order Protactiniae which 

 is based on this feature. It may be noted that this order is 

 much more comprehensive than Carlgren's Protantheae, and 

 in view of our present more complete knowledge of the forms 

 in the past associated in the family Halcampida?, I would even 

 suggest the propriety of increasing its comprehensiveness by 



