480 
PROTOZOA. 
A. Metzgeb enumerates 1 Myxocystodeum^ 3 Spongice, and 4 Rhizopoda as 
occurring on the E. Friesland coast : JB. Ges. Hannov. xx. pp. 35, 36. The 
species of Rhizopoda found by Ehrenberg and Harting in the mud of the 
rivers of the district are also enumerated. 
SPONGIIDA. 
II, A. Pagenstecheb (^‘ZurKenntniss der Schwiimme,” Verh. Ver. Heidelb. 
vi. pp. 1-66) reviews the principal works on Sponges and systems of classi- 
fication (which he reproduces very fully) from Aristotle to the present time, 
E. Hackel (^^Ueber die sexuelle Fortpflanzung und das natiir- 
liche System der Schwiimme/^ Jen. Z. Nat. vi. pp. 641-651) 
mentions that the number of species of Calcispongim known to 
him in 1869 has now been more than doubled. During a visit 
to Dalmatia he has succeeded in detecting zoosperms in sponges 
of the groups Ascones, Leucones, and Sycones, and also in some 
siliceous sponges. The zoosperms of sponges are simply modified 
flagellated cells of the entoderm, the ciliated epithelial layer of 
cells which arises out of the inner germinal layer. Some cells 
of this layer retract their flagellum and become ova, others 
zoosperms ; but in many calcareous sponges the zoosperms and 
zoospores can with difficulty be distinguished from each other. 
The development of the zoosperms, and the phenomena of con- 
jugation are fully described. The sponges are hermaphrodite, 
zoosperms and ova always coexisting in the same individual. 
These observations establish the relationship of the sponges to 
the Coslenterataj and completely disprove their supposed rela- 
tionship to the sexless Protista or Protozoa. The flagellated 
sponge-particles of the entoderm of calcareous sponges fre- 
quently change into amoeboid cells, and sometimes vice vei'sd. 
Decided pseudopod formation takes place (only?) in the cal- 
careous sponges, the ectoderm being sometimes covered with a 
tliick down of extremely fine hairs, especially in the ectoderm- 
sheaths which enclose the isolated spieules. Hackel has also 
succeeded in discovering the natural system, i. e. the genea- 
logical tree, of the calcareous sponges, and has been able to 
follow, step by step, the genesis of their species. All former 
systems are artificial; but Hackeks 3 groups ilficroporew/a, Cla- 
doporeuta, and Orthoporeuta are natural {Aporeuta, founded on 
Prosycum, proves to be only a transitional form of Olynthus ) . 
Hackel renames these groups : — (1) Ascones. Gastric wall very 
simply permeated by inconstant dermal pores. Corresponds on 
the whole to the Grantice of Lieberkiihn, or the Leucosolenice, 
Bowerb. Types, Grantia [Leucosoleraa) botryoides and G. co- 
riacea : nearest the Hydroida. (2) Leucones. Gastric wall 
very irregularly permeated by tortuous and ramifying vessels , 
( = Granti(Ej Schmidt; Leuconice, Bowerb.; including the Leu- 
coyypsioi). Types Grantia (Leuconiu) nivea and G. solida. 
