326 Mr. H. J. Carter on the 



to the fully developed embryo, whose colour seems generally 

 to accord with, and be more intense than, that of the parent 

 sponge, although in Ilalichondria simulans it is opaque white ; 

 while the upper part of the sponge becomes atrophied into a 

 mere capsular layer (especially in Ilalisarca lobularis)^ and 

 the vents appear to be in direct communication with the 

 branches of the excretory canal-system, now expanded into 

 common coverings for the heaps of ova respectively, which 

 thus enables the embryos, when fully formed, to make their 

 exit without difficulty. The position, in point of aggregation, 

 of the ova in these sponges corresponds with that of most 

 species of Spongilla ; still, in some species of the latter, as 

 well as in some of the marine siliceous sponges, they appear 

 to be diffused throughout the mass — perhaps after all, how- 

 ever, being most plentiful about the base or oldest-formed 

 portions of the sponge. While, therefore, in many instances, 

 if the piece of rock on which the oviparous sponge, in this 

 stage, may be grooving is not broken off with it, the upper 

 portion alone may be taken, and thus the ova escape observa- 

 tion. At the same time, almost all the specimens of Halisarca 

 lohularis which 1 obtained on the 29th August, having been 

 reduced to mere surface-shells, in which the red-violet colour 

 of the spongozoa was unusually intensified, and from which 

 the whole of the ova, having passed into the locomotive 

 ciliated embryos, had escaped, and had thus left them hollow at 

 the base, indicated that this date is too late for finding Hali- 

 sarca lohularis in that oviparous condition which is requisite 

 for following the development of the ovum. 



To obtain the ova for examination it is absolutely neces- 

 sary to tear the mass to pieces, and either examine them {71 

 situ^ or seek for those which may have fallen out entire ; while 

 a few of the ciliated embryos that are far advanced may also 

 thus be forcibly eliminated. 



But, to obtain the embryos in a fully matured state, either 

 in Halisarca lohularis^ HalicTiondria simulans^ or Qrantia 

 compressa, it is best to place the oviparous specimens of these 

 sponges respectively in this stage of ovi-development in sea- 

 water uninjured, and let the embryos escape by themselves 

 natui-ally. This can be done by breaking off a portion of the 

 rock on which the two former sponges may be growing, while 

 with Grantia compressa it is only necessary to cut off the 

 branch of Ptilota to which it may be attached. 



Having thus got out a sufficient number of embryos for im- 

 mediate examination and the study of their subsequent develop- 

 ment, we have only to transfer them, by means of a pipette, 

 to any convenient place for this purpose. In doing this, the 



