60 



GOMPABATIVE ANATOMY 



CHAP. 



between these consists of branched and partly anastomosing cells, 

 wbicb lie in a hyaline ground substance. The cells of the lowest layer 

 possess processes, which pass into the processes of the cells of the 

 middle layer without sharp distinction. As long as we have no know- 



FiG. 55.— Part of a vertical section through tlie body of Triclioplax adlisereiis, after 

 P. E. Scliulze. 



ledge of the reproduction and development of this animal, judgment 

 as to its morphology must be suspended. 



[Note. — Of. p. 175. Where the author suggests that the Dicyemidce and Ortho- 

 ncdidce, on account of their similarity to the sporocysts, are degenerated Trematocla. 

 -Tr.] 



Literature. 



E. Haeckel. Biologische Studien. Heft II. 1877. 



Ed. van Beneden. Becherches sur Us Dicyemides. Bull. AccuUniie Belgique. 



Bruxelles, 1876. 

 C. O. Whitman. A Contribution to the Embryology, Life-History, and Classification 



of the Dicyemids. Mittheil. aus d. zool. Station zu Neapel. T. IV. 1882. 

 A. Giard. Lcs Orthoneetides. Journal de I'Anatomie et de la Physiologie. T. XV. 



1879. 



E. Metschnikoff. Untersiochungen ilbcr Orthonectiden. Zeitschr. f. wiss. Zoologie. 



Bd. 35. 1881. 

 Julin. Contribution A I'histoire des Mesosoaires. Archives de Biologic. T. III. 

 1882. 



F. E. Schulze. Ueber Trichoplax adhaerens. Zoolog. Anzeiger. Bd. VI. 1883. 



S. 92-97. 



Class II. Porifera or Sponges. 



Systematic Review. 



Sub-Class I. Calcaria. — Skeleton composed of spicules of carbonate of lime, 

 always present. According to the structure of the soft body, Ascones, Syeones, and 

 Leucones. Olynthus, Ascandra, Sycandra, Leucaiulra. 



Order 1. Caloispongise. 



Sub-Class II. Non-Calcarea. — Skeleton seldom wanting, but never of calcareous 

 spicules, rather of siliceous spicules or spongin fibres. According to the structure of 

 the soft body, Leucones. 



