and the Winter-egg of the Bryozoa. 337 



I have not been able to detect a ciliated envelope on the ovum 

 of Spongilla ; but it is very probable, from the ciliated character 

 of this organism generally, that there may be one here also in 

 the early part of its development; while the first appearance of 

 the ovum itself, as a white point consisting of a transparent 

 capsule filled with a few spherical transparent cells charged with 

 refractive granules, and its subsequent development in all stages, 

 so correspond with those of the winter-egg of the Bryozoon, that 

 the most scrupulous observer can hardly object to their being 

 considered essentially homologues. 



Thus we are now enabled to see the resemblance of the struc- 

 ture surrounding the ova of Spongilla Meyeni and S. phnnosa 

 (which I have long since shown to consist of an incrustation or 

 coat of amorphous matter, and short straight amphidisk-spicules 

 arranged vertically on the coriaceous coat*) to the cellular coat 

 of the winter-egg of the Bryozoa. 



We have yet, however, to compare the development of Spon- 

 gilla and Lophopus as they issue from these ova respectively ; 

 and this brings us back to the consideration of the question 

 whether the piece of Spongilla, as I have described it, and as it 

 always appears after exit from the ovum of Spjongilla, is to be 

 regarded as a congeries of animals or a single one. If we wish 

 for an instance of a plurality of individuals in an allied organism 

 being developed from a single ovum at once, we have it in the 

 three which issue at once from the winter-egg of Lopjhopus cry- 

 stallinus, which are contained nnder the same tunic or in the 

 same pouch f; if where the ovum sends forth six or seven 

 embryos at the same time, but separate, we have it in the q^^ 

 of Nais filiformis, &c. If, on the other hand, we are to regard 

 these as so many buds on a common stock, or flowers on a plant, 

 then must we regard the typical portion of Spongilla described, 

 as a single animal. The real nature or homology of the spherical 

 bodies attached to the branch of efferent canals, however, not 

 being yet established, it would be useless now to carry this 

 comparison further. 



Of what import arc the refractive granules in the spherical 

 transparent cells of the ovum of Spongilla and the winter-egg of 

 the Bryozoa, is another interesting question. Undoubtedly the 

 former with their budding closely resemble the refractive yelk- 

 granules oi Nais fusca%, while they are equally like the refractive 

 cells and granules of the Eiiglence^, and also those of the resting- 



* Annals, vol. iv. pi. 3. fig. 6, 1849. 

 t Dumortier and Van Beneden, op. cit. ])1. 6. fig. 24. 

 + Annals, vol. ii. p. 13, ^\. 3. fig. 51, 1858. 



§ Annals, vol. xvii. pi. 9. fig. 11 ; vol. xviii. pi. 6. fig. 56; and vol. xx. 

 pi. 1. fig. 16. 



Ann. S^ Mag. N. Hist, Ser.3. Vol 'in. 23 



