Bibliographical Notices. 133 



vering experimentalist was mentioned by those who write for the 

 public ; and foreigners were compelled, almost reluctantly, to ac- 

 knowledge that the Scotch savans had been for years familiar with 

 facts and phenomena, for the discovery of which, in a less perfect 

 manner, they were seeking the praise and honour of their competi- 

 tors. The present publication will not only prove Sir John's inde- 

 pendent discoveries and priority, but it will place its author in the 

 first rank of those who gain deserved honour by their talent for ori- 

 ginal observation, and by that devoted love to a subject which car- 

 ries one unwearied through years of patient experiment, heedless of 

 any future reputation, and regardless of being forestalled by the fear 

 of anticipation which urges on too often to hasty publicity. 



In our present notice we shall confine ourselves to the Hydroid 

 Zoophytes. And were we to distinguish these according to diver- 

 sity in their embryology, the researches of Sir J. G. Dalyell would 

 enable us to divide them into three families, viz. (1.) those which 

 " propagate the young in their own likeness by gemmation or bud- 

 ding from the side ;" (2.) those which in the foetal or larva state re- 

 semble the Medusa ; and (3.) those which produce an unciliated 

 roundish corpusculum, that, on its escape from the ovarian vesicle, 

 assumes the shape and motions of the Planarice. 



The first family is limited to the freshwater Hydra?, and need not 

 now detain us, excepting only to remark that our author appears 

 never to have observed these polypes to propagate by any other 

 means than by gemmation. Their winter eggs, described by others, 

 do not seem ever to have come under his notice. 



The species of the second family ascertained to be so by our 

 author are Tubularia indivisa, T. larynx, T. ramosa and Laomedea di- 

 chotoma. The similarity of their larva? to miniature Medusa? in form, 

 in structure and in habits is so very remarkable, that, even after 

 having witnessed their progressive development and birth from the 

 parent, Sir John can scarcely bring himself to admit their relation- 

 ship. But there can be no doubt of this, and the metamorphosis is 

 one of the most wonderful in the animal kingdom. We know not 

 that we could make more distinct to our readers the idea of these 

 larva? than by the comparison of them to Medusa? which has just 

 been made, and must therefore refer to the volume itself for the full 

 details. The interest of the zoologist will not flag in their perusal, 

 and in the examination of the figures ; although there is certainly 

 wanting that precise and regular specification of embryotic changes 

 which distinguishes the memoirs of Van Beneden. 



The third family embraces Tubularia ramea, Thoa halecina and 

 Beanii, Sertularia polyzonias, abietina, rosacea, pumila, argentea and 

 arcta, Antennularia antennina and ramosa, Plumularia falcata and 

 pinnata, and Campanularia verticillata. All these produce a roundish 

 oviform body, which on, or even previous to, its eduction from the 

 ovarian receptacle assumes the figure of the worms of the genus 

 Planaria. Hence it is called a.pla?iule by our author. It appears to 

 be an immediate evolution from the central pulp, the colour of which 

 it has on its birth ; but some species produce planules of at least two 



