856 APPENDIX. 



ordinary interest since it serves to unite the anomalous genus Ophryodendron with 

 the more typical Acinetidae. This is more especially manifested in connection with 

 its possession of a membranous lorica, and in the non-development of motile cirri 

 at the extremity of the single proboscidiform tentacle. This tentacle, moreover, 

 in addition to its simple structure, coincides in the circumstance of its delicate 

 externally developed spiral fibrilla with the slender prehensile tentacle oi HeiniopJuya 

 gcmmipara. Taken as a whole, the general structure of Acmetopsis would appear 

 to be not so very remote from that of Urnula ; it is an open question, indeed, 

 whether the two extremities of the Tentaculiferous series might not be consistently 

 united at this point. The act of food-ingestion, as in the case of Ophryodendron, 

 has not as yet been witnessed, but it was observed that the extended tentacle was 

 capable of motion in every direction. The resemblance subsisting between a 

 zooid of this species and the peculiar thecated sarcodic appendages, the so-called 

 " nematophores " of certain Hydroid zoophytes, has been referred to at page 805. 



APPENDIX TO VOL. II. 



Notice of Supplementary Species and more important Discoveries con- 

 cerning THE Infusoria recorded during the Publication of this 

 Work, or accidentally omitted from insertion under their respec- 

 tive headings. 



Class I. Flagellata. 



Genus Dimorpha, Gruber. — Animalcules free-swimming, dimorphic, reverting 

 at will from a Heliozoidal or Actinophrys-like phase to a simple monadiform condi- 

 tion, or vice versa; in either state bearing two long, closely approximated vibratile 

 flagella. 



Dimorpha mutans, Gruber. — Zooid in its monadiform condition symmetri- 

 cally ovate, wider and somewhat truncate at the anterior border, tapering gradually 

 towards the posterior extremity ; flagella subequal, about twice the length of the 

 body, inserted close to each other near the centre of the anterior border; paren- 

 chyma tiansparent near the front margin, granular throughout the remaining area, 

 usually enclosing digested food-substances in the posterior region of the body; 

 contractile vesicle single, subcentral ; endoplast imperfectly observed. In its 

 Actinophrys phase, the body spheroidal or slightly elongated, bearing in addition to 

 the two vibratile flagella numerous slender, finely granular, ray-like pseudopodia, 

 having a fully extended length of two or three times the diameter of the body, and 

 which decussate from the periphery in every direction. Diameter of body of 

 Actinophrys-like phase 1-1600". Hab. — Fresh water. 



This highly interesting species, recently figured and described by Dr. August 

 Gruber,* was obtained by him in some abundance from a slowly flowing canal in the 

 neighbourhood of Lindau. As rightly inferred by its discoverer, it constitutes an 

 intermediate or annectant type between the respective groups of the Flagellata and 

 the Heliozoarian section of the Radiolaria. It is indeed very closely allied to the two 

 marine forms, apparently unknown to Dr. Gruber, figured and described by the 



* ^^ Dimorpha mutans, eine Mischform von Flagellaten und Heliozoen," ' Zeitschiift fiir Wissen- 

 schaftliche Zoologie,' Band xxxvi. Heft 3, December 1881. 



