1012 SUMMARY or CURRENT RESEARCHES RELATING TO 



becoming grouped round one or more mesoderm cells as centres. 

 Eound each clump or pseudomorula of nutritive cells a thin cuticle 

 is differentiated, outside which the mesoderm forms an endothelium 

 in which the horny and flinty materials of the capsule appear. After 

 the formation of the gemmulse the mesoderm degenerates, and by the 

 end of autumn the whole Spongillse usually breaks up. 



(&) Structure and escape of the embryo. — The embryo within the 

 capsule is at first a morula-like mass of round uniform cells, with 

 abundant food-granules. With inception of water the cells become 

 polyhedral through the mutual pressure of growth, and gradually 

 come to form a mass with indistinguishable cell-boundaries. The 

 further growth of this syncytium is marked by the protrusion of a 

 large pseudopodium from the " microdiode," " omphaloporus," or 

 capsule aperture. This process probably increases in size till it 

 draws the rest of the embryo out with it. The sponge embryo 

 escapes from the capsule in April or the beginning of May, and has 

 the form of a flattened sphere, in which it is possible to distinguish 

 the cells both of the clear ectoderm and of the granular inner sub- 

 stance, the endoderm. In most cases the young sponge remains 

 seated for twenty-four hours or so on the forsaken but still intact 

 capsule, over which the clear outer sheath sends out pseudopodia, 

 which are probably effective in abstracting from the gemmula the 

 rudiments of the flinty skeleton of the embryo. 



(c) Further growth of the liberated embryo. — After leaving the 

 capsule the embryo increases in size at the expense of the store of 

 nutritive granules in the inner mass. It exhibits no demonstrable 

 power of active locomotion, and after floating about, in some cases for 

 two days, it settles down and exhibits a series of further changes, of 

 which the details seem to be somewhat variable, the characteristic 

 processes of other sponges being here united in the one form. In the 

 internal mass or coenoblast an enteric cavity is developed either with 

 or without, and either before or after osculum and inhalent apertures. 

 By the end of May or first half of June the young Spongillse are 

 sexually mature, and that unisexually. It seems probable that the 

 males are destitute of enteric cavity and mouth, with both of which 

 the more abundant and more spheroidal female forms are usually 

 provided. From these spring sexual forms the summer Spongillse 

 are developed in a manner closely resembling that previously de- 

 scribed in the case of Beniera jiligrana. After fertilization the males 

 seem to perish, while the females after bearing the neuter forms 

 increase greatly in size till about the beginning of August, during 

 which growth the enteric cavities and mouth-openings are reduced in 

 size and not unfrequently disappear. There is thus in Spongilla 

 lacustris a seasonal alternation of generations ; the winter gemmulsB 

 form spring sexual Spongillse, which produce asexual forms in which 

 arise the winter gemmulse. 



The Phoriospongise.* — Dr. E. v. Lendenfeld has obtained in 

 Australia the two sponges described by W. Marshall as repre- 



* Proc. Linn. Soc. N.S. Wales, x. (1885) pp. 81-4. 



