Bibliographical Notices. 349 



the reproduction of those Freshwater Algae in which zoospores 

 form the commonest means of propagation. From the recogni- 

 tion of the contemporaneous existence of zoospores or gonidia 

 with sexual organs of reproduction in Vaucheria, he is led to 

 conjecture the existence of a similar condition in other genera. 

 In Achlya, both zoospores and resting spores are known, and he 

 suspects that the slender branches found upon those filaments 

 of Achlya which bear sporanges, will prove to be antheridia. 

 In CEdogunium, the membrane of the sporangial-cell bursts 

 before the formation of the spore-coat, which admits of the 

 possibility of a penetration of spermatozoids. In Bulbochcete, a 

 fissure is also met with. Now in these genera, besides resting- 

 spores and ordinaiy zoospores, we find exceedingly small bodies, 

 resembling the zoospores in their structure, called by A. Braun 

 microgorddia. These are developed in cells smaller, and differ- 

 ing in character from the ordinary vegetative cells. They 

 germinate, but produce small bodies, composed only of one or 

 two cells, which, it is remarkable, are always found attached 

 upon the sporangia, or near them. Here they dehisce and 

 discharge their contents. Although no trace of spermatozoids 

 has been perceived in them, this discharge of the contents near 

 the opening of the sporangial membrane tends to the conjecture 

 that they exercise an impregnating influence on the resting- 

 spore. If this be the case, we should have the curious phse- 

 nomenon of the male structure being developed as a special 

 separate body, a kind of prothallium. With the above peculi- 

 arities is associated in Bulbochate a curious mode of germination 

 of the resting-spores. Examples of these kept through the 

 winter produced, not a new filament, but four ciliated zoospores, 

 which escaped, came to rest, germinated, and then produced 

 new filaments. A similar phsenomenon was observed in the 

 case of the resting-spores of Coleochate. 



The paper concludes by a summing up of the results, which 

 will be unnecessary after this brief abstract. 



BIBLIOGRAPHICAL NOTICES. 



A History of the British Marine Testaceous MoUusca, distributed 

 in their Natural Order. By William Clark. London : Van 

 Voorst, 1855. 



The study of malacology, or of the true natural historj' of the 

 MoUusca, has sprung up almost entirely within the last half-century. 

 Up to this period the attention of zoologists in this department was 

 almost exclusively directed to the shells of these animals, the only 

 part which admits of being easily preserved in the cabinet or trans- 

 ported from a distance, and the structure of the creatures producing 



