174 



PROF. ST. GEORGE MIVART ON 



universally, present in the group. Anyhow, I would make its pre- 

 sence or absence a primary character, and therefore follow Hertwig 

 in separating off from Haeckel's Collida those forms which have 

 the nuclear vesicle, and uniting them with the other genera which 

 possess that structure into a group of Vesiculata. His remaining 

 Collida (namely, TJialassospJicBra and Thalassoplaneta) I would 

 associate along with Haeckel's Polycyttaria into a group under 

 the name Collozoa. 



His AcantJiodesmida, Cyrti'la, and Ethmosphcerida may then be, 

 I venture to think, associated together as ectolithic, non-vesicu- 

 late, simple forms, the skeleton of which consists of more than 

 detached spicula ; and to this group the old name of Poltctstina 

 may well be applied. 



A very important and natural character seems to me to be the 

 possession of a large flagellum ; and I would therefore propose to 

 unite in a group of Flagellifera the genera Spongocyclia* , Spon- 

 godiscus, and JEucliitonia. 



The meeting together of radii in the centre of the capsule 

 seems to me a very special and peculiar condition ; and I therefore 

 regard as unnatural the separation from the thus characterized 

 Acanthometrida of forms (Haeckel's Dorataspida-f) which differ 

 only in having tangential outgrowths from their radii so disposed as 

 by their mutual junction to form an external shell. I would there- 

 fore restore to the AcantJiometrida those of Haeckel's Ommatida 

 the radii of which thus centrally meet, as a separate subsection, 

 to which I would restore the old name Cataphracta^ to distinguish 

 them from the more Acanthometrine forms, or Typica. 



Again, Biploconus, as presenting the special character of cen- 

 trally-joined radii, I would unite as a third section of the same 

 great group, regarding its conical structure as a mere special mo- 

 dification of radial structure. 



The remainder of Haeckel's Ommatida I would propose to 

 unite with his Coelodendrida and Cladococcida, as forms possessing 

 an intracapsular more or less spheroidal shell. Moreover I 

 cannot regard the possession of a spongy skeleton as a natural 



* Though Haeckel failed to find this curious organ in two species of S'pongo- 

 cyclia (namely, in *S. cycloides and 8. elliptica), yet, as it is present in all the 

 seven species of Euchitonia, I cannot but think its absence may have been due 

 to some accident, or, at least, that such absence cannot be a character of those 

 two species at all times. If, however, it should turn out to be constantly absent 

 in them, then I think those two species should be eliminated from the group. 



t L. c. p. 239. 



