398 Mr. II. J. Carter un the 



previous to further development, as may be done with that of 

 the embryo of Halichondria simulans, which, from its great 

 size and opaque white colour, may be seen even with the un- 

 assisted eye. But the facts of the great resemblance between 

 the two, and their habit of attaching themselves now and then 

 to the bottom of the glass vessel or to foreign objects Ly 

 the truncated or wnciliated end while in locomotion, and the 

 latter having been actually seen to fix itself by the truncated 

 end for further development, while the subsequent develop- 

 ments are the same in both cases (that is, into the respec- 

 tive parent structures), render it more than probable that the 

 settling down and disappearance of the cilia, which is the onl^ 

 point in the development of the calcareous sponges that has 

 not been observed, is also the same as that of the siliceous 

 sponges. 



Since the above was written, I have seen a short article, 

 with illustrations, on the development of the embryo of the 

 Calcispongige by E. Metschnikoff, in Siebold and Kolliker's 

 * Zeitschrift fiir wissensch. Zoologie ' (Band xxiv., erstes Heft, 

 p. 1, Taf. i., published on the 12th of February last), wherein 

 I am pleased to find that the author has inserted what Hiickel 

 has omitted, and that my own views and figures on this subject 

 liave been anticipated, but so much more sequentially and 

 completely given that they are of far more consequence to the 

 student than my own. Not less so tlie second part of the 

 article, wdiich is devoted to a sharp criticism on Hiickel's 

 statements in ' Die Kalkschwamme,' and, coming from such 

 high and practical authority as Metschnikofi^, merits a con- 

 fidence which even the uninspired Historian of the Creation 

 fails to command ; that is, it is 7-es non verba ! 



From the almost identity of Metschnikotf' s single figure of a 

 "i?e/^^era-Larve," obtained in the Crimea, with mine of Hali- 

 chondria simulans =Reniera palmata, Sdt. (?), fomid here, it is 

 just possible that both came from the same species of sponge. 



Emhryos of Halisarca lobularis. 



Returning to Halisarca lobularis^ there are yti two figures 

 of the embryo of this sponge among the illustrations which, 

 as before stated, I have purposely omitted to notice, since at the 

 time of describing the development of the ovum in this sponge 

 up to the ultimate degree of duplicative subdivision, or to the 

 end of the second pei'iod of development, it was desirable not 

 to go further. 



The first of these figures (PL XX. fig. 11) represents the 

 embryo at that stage in which the spheroidal ovum has become 

 elongated into an ovoid shape, covered throughout by the 



