THE RETROSPECT. 



39 



birds, shot in the neighbourhood, of Dunbar, by Mr. Sinclair, and prepared by him for cabinet 

 specimens, in a style seldom equalled. 



Mr. Geokge Donaldson exhibited two specimens of the Common Yellow-hammer, (Embcriza 

 citrinella,) remarkable varieties, entirely of a pure yellow, except the quill feathers, which 

 were pure white. These birds were killed in tlie isle of Gomctra. 



Mr. Roger IIexnedy then read the following remarks upon the Algae developed on the 

 House-fly: — "Some excuse might be considered necessary in introducing to your notice the 

 present plant, as, coming after Mr. Napier's observations, it may appear obtrusive; but when 

 we consider the plentiful appearance of the fly, with its accompanying parasite, during the end 

 of summer and autumn, and its nature not being generally known, I have been induced to 

 bring the following remarks before you. To describe the difference betwixt Alga) and Fungi 

 is rather a dfiicult task, although the mere tyro can generally distinguish the one from the 

 other in the fields. Fungi may be described as aerial plants, seldom or never being found 

 growing in water, and are almost universally developed on decaying animal and vegetable 

 substances. On the other hand, Algae are always found in liquids, or in moist places; in the 

 sea, they are found growing on rocks, shells, or parasitically upon members of their own 

 family. The present plant from its definition— if definiuion it can be called, bears an anomalous 

 position, partaking of both characters; in it we have a development on animal substances, 

 being found upon dead flies, and live gold fish in water, and upon the former as an aerial 

 plant. If it belongs to the Fungi, its great peculiarity consists in bearing zoospores, which 

 none of this class have been known to do. In most of the lowest forms of Algae we find 

 this mode of reproduction. Good specimens of this plant may be procured by putting newly- 

 killed flies in water, and allowing them to remain for a few days." 



Here Mr. Hennedj' described the plant as developed upon the fly as it clings to the wall; 

 he stated that in that position the plant makes its appearance between the rings of the 

 abdomen, which are then very much swollen. He then went on to detail the mode of 

 development on a fly immersed in water, with the time necessary to perfect the growth of 

 the plant; the following is his own description of h's experiment: — "On Thursday evening 

 October 7th., at five o'clock, I put a fly, newly-killed, in some water, in which some oscil- 

 latorias were growing; on the next evening, Friday, there was no appearance of any plant, 

 but on Saturday evening at the same hour, five o'clock, the plant was grown larger than 

 ever I had seen it when developed as an aerial specimen — it gave the fly quite a woolly 

 appearance. By Monday it had grown fully longer in proportion to the fly, than the one 

 drawn on the board; on Tuesday it was sent to a friend, but before doing so, I tried if 

 another fly in the same water, inoculated with the old plant, would produce it anj' quicker; 

 this done, at the same time I took some of the Glasgow water fresh drawn from the pipe; 

 and inimei-sed in it another fly; this was Tuesday evening, October 12tli., at five o'clock. On 

 Wednesday, at eight o'clock, visible signs of milky points protruding from the body of the fly 

 were perfectly visible. On Thursdaj' evening the plant was well-grown, thus taking two days 

 to perfect its growth. While all this was going on, no appearance of vegetation was visible on 

 the fly in the pure water; in three days growth had commenced — visible in the morning at 

 half-past eight o'clock, but by eight o'clock in the evening the plant was well-grown. Of 

 its quickness of growth, it is mentioned in an article "On the Escape of the Zoospores 

 of Algas," in the French Annals of Natural Science, that a visible growth takes place 

 even during the short time they are under the microscope for examination. The fol- 

 lowing are the names by which this plant is known: — Saprolegnia ferax, Kutz; Vaiicheria 

 aquatica, Lyng; Achlija prolifera, Saprolegnia miiscorum, Nees; Leptomitus davatus, Ag." 



Mr. David Kobertson wos elected a resident member. 



€\}t lUtrDSjirrt. 



We are induced, after some consideration, to open a portion of our pages under the above 

 title, for the examination of previous articles in "The Naturalist," more particularly with a 

 view to the correction of any errors or mistakes which may have been promulgated in them. 

 We anticipate much benefit from such articles, and only request that in no case may anything 

 approaching to personality be introduced ; by observing this rule, the ends of science will be 



