564 PROTOZOA. 
12. Hyatt, A. Revision of the North American Porifer(x, with remarks 
upon foreign species. Pt. I. Mem. Bost. Soc. ii. pp. 1-10, pi. xiii. 
(Preliminary note in P. Bost. Soc. xiii. pp. 204 & 205.) 
13. Kustermann, H. Hyalonema sieboldi, Gr. Arch. mikr. Anat. xi. 
pp. 286-291, pi. xvi. 
14. M.^rshall, W. Untersuchungen uber Hexactinelliden. Z. wiss. 
Zool. XXV. (suppl.) pp. 142-243, pis. xi.-xvii. 
15. Meyen, a. B. On Hyalonema with a note by Mr. Higgin. 
Ann. N. H. (4) xvi. pp. 76 & 77. 
16. Schmidt, O. Spongien. JB. Comm, zur wiss. Untersuch. der 
deutsch. Meere, ii. & iii., pp. 115-120, pi. i. (abst. Z. ges. Naturw. 
xii. pp. 173-181). 
17. . Zur Orientirung iiber die Entwickelung der Spongien. Z. 
wiss. Zool. xxv. (suppl.) pp. 247-280, pis. xviii.-xxi. 
18. Schulze, F. E. Ueber den Bau und die Entwickelung von Sycan- 
dra raphanus, Hackel. Z. wiss. Zool. xxv. (suppl.) pp. 247-280, 
pis. xviii.-xxi. 
19. Wright, P. Report on the structure and mode of life of Hyalo- 
nema lusitanicum^ Bocage. P. R. Irish Ac. (2) i. pp. 549-552. 
Ancf^tomy, Evolution. 
Through Schulze’s studies of the anatomy of Sycandra (18), the pre- 
vailing ideas on the histo-morphology of sponges are once more modi- 
fied. He distinguishes, as in Coelenterata, 1, a single layer of flagel- 
late endodermal cells, investing the cavities of the radial tubes; 2, a 
mesodermal hyaline layer, with imbedded stelliform and amoeboid cells ; 
in this layer the spicular skeleton is formed, and here also —not from the 
endoderm — the eggs are formed, probably from the amoeboid cells ; 3, an 
ectodermal unicellular plate-epithelium, investing the external and in- 
ternal surfaces, and the intercanaline cavities. 
Schmidt (17) confirms some of Metschnikoft’s [Zool. Rec. xi. p. 532 ; 
Q. J. Micr. Sc. xv. pp. 78 & 79] observations on the evolution of Cal- 
cispongice ; the Sycandra-ldiVYdi is composed of 2 portions, an anterior, 
formed of prismato-conical flagellate cells, and a posterior, of large not 
flagellate globules. There is a small central cavity, but no mouth, 
and the body-wall is only formed of a single cell layer. “ Therefore 
there is no “ Gastrula*' and the presumed importance of this stage breaks 
down with all the beautiful theoretical conclusions.” According to 
Schmidt’s observations on other genera of sponges, generalizations are 
still premature, thie observations contradicting each other ; the “ plano- 
gastrular ” larva of Ascetta is formed of a single ciliated cell-layer, &c. 
Schulze (18) however shows that Hackel’s ideas are somewhat nearer 
the truth ; he pursued the egg through all stages of transformation 
and cell multiplication down to the stage observed by Schmidt and 
Metschnikoff ; a “ Gastrula ” is really formed through the invagination 
of the posterior, non-ciliated portion of the larval body, the large 
