Miscellaneous. 7o 



in the parenchyma of the endoderin, and at once enter into commu- 

 nication with them. 



This parenchyma, or the whole non-epithelial cell-mass of the 

 sponge, has essentially the same structure as in the larva ; the 

 rounded or stellate cells are suspended, by means of their mutual 

 attachments, in a fluid, which at first also occupied the great endo- 

 dermal cavity and its processes, but afterwards becomes somewhat 

 condensed within the tissue, while, in the cavities which open out- 

 wards, it is displaced by water. The spicules, which always origi- 

 nate intracellularly, are also already present in the larva. 



A brief recapitulation of the described facts shows that — 



1. The bilamellar embryo is a sterrogastrula, which afterwards 

 acquires an endodermal cavity. 



2. The ectoderm entirely disappears during the attachment of the 

 larva ; the future sponge, with all its parts, proceeds entirely from 

 the endoderm. 



3. This early divides into a peripheral layer, which becomes an 

 epidermis in place of the ectoderm, and a compact interior mass, the 

 foundation of all the other tissues. 



4. In the latter the incurrent and exhalent cavities and the 

 flagellate chambers, as well as their linings, originate separately 

 without any common foundation, so that the distinction of an entero- 

 derm from a mesoderm is not possible. 



5. The Spongillce, as indeed all the sponges, originate from 

 " bilamellar " ancestors ; but at present develop their whole organi- 

 zation from a single germ-plate. — Zoologischer Anzeiger, December 

 15, 1884, p. 076. 



Note on the Reproduction of the Monotremata. 



To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, — Aproposot Sir Richard Owen's paper in the Ann. & 

 Mag. Nat. Hist., for December last " On the Impregnated Uterus and 

 on the Uterine Ova of Echidna Tiystrix" accompanied by a copy of a 

 letter from the 'Sydney Herald' announcing Mr. Caldwell's most inter- 

 esting confirmation of Owen's researches by anatomical proof of the 

 oviparous reproduction of the Monotremata, I beg to send you the 

 following extract from the 'Illustrated Melbourne Post' of Sep- 

 tember 24, 1804, which was reproduced in the ' Zoologist' for 1805, 

 p. 9431 :— 



"Eggs of Ornithorhynchus. 



" About ten months ago a platypus (Omithorhu nchus paradoxus) 

 was captured, and is in possession of Mr. Rumley, gold-receiver, 

 of Woods Point. It has laid two eggs, which were white, soft, and 

 without shell. It is to be regretted that no opportunity was afforded 



