12 



HARDWICKE'S SCIENCE- GOSSIP. 



to twig, the close observer will notice it always 

 alights with a peculiar jerk of the body from one 

 side to the other. It feeds chiefly on small cater- 

 pillars, moths, and butterflies, and is also a great 

 devourer of small fruit, such as red currants, rasp- 

 berries, strawberries, and elderberries ; in the 

 cherry season its beak is generally stained with 

 cherry -juice. The nest and eggs are scarcely dis- 

 tinguishable from those of the Blackcap : it is the 

 true Beccafico of the Italians, and by them it is 

 killed and eaten in large quantities. 



In confinement this bird, though more easily 

 tamed than the Blackcap, is a more tender bird, 

 rarely living more than four or five years. All that 

 I have said concerning the Blackcap on page 79 

 of the last volume applies equally well to the 

 Garden Warbler. In addition to the food there 

 mentioned, there should always be a tin of rasp- 

 berry or red currant jam in its cage ; it is also foud 

 of boiled green peas, grape-juice ; and a piece of 

 lump sugar in its water is a great treat to it. In 

 the moulting season give it mealworms or ants' eggs 

 every day ; it is very fond of elderberries, which 

 may be dried in the season, and then kept all the 

 year round ; and when wanted, boiling water must 

 be poured on them, and when cold drained off, and 

 in this way they swell out, and are as good as fresh 

 berries; dried ants' eggs may be treated in the 

 same way. 



If fed on little but rusk sop, its feathers fall out, 

 and in winter it dies of starvation ; it should have 

 plenty of variety, and if well fed and cared for, it 

 will sing almost incessantly from November to 

 June. It is more susceptible of cold than any 

 other cage bird, and continued wet weather has a very 

 marked depressing effect upon it. In warm weather 

 a bath three or four times a week may be given it, 

 but in winter this must not be given, as the bird 

 would be seized with cramp, and die in a very 

 short time. — /. S. Metcalfe. 



THE ECONOMY OE THE FRESH- WATER 

 POLYP. 



IN the June number of Science-Gossip, 1S72, 

 page 132, was published (with illustrations) a 

 communication from me on the above subject, in 

 which I endeavoured to describe what I had observed 

 of them. The question that arose in my mind at 

 the time, as to what the nature of those objects was 

 seen to spring out with considerable force from 

 certaui protuberances on the body of the Hydra, 

 has been satisfactorily answered, and proved to be 

 spermatozoa. As the power of my microscope was 

 not great enough to define their form, I could only 

 discern them as very minute and indistinct particles. 

 I therefore gave some of the polyps to George 

 Gulliver, Esq.,E.R.S., and he examined them under 



an objective (Powell & Lelaud) of one-teuth of ar. 

 inch focal length, and found the spermatozoa very 

 active. 



Mr. Gulliver estimates the mean length of each 

 spermatozoon at about -gioo of an inch. I have 

 continued to follow up the study of these interesting 

 animals, and on June 1st, last year, I had a number 

 of Hydra viridis in my aquarium, and on closely 

 examining some of them, 1 observed on them the 

 same form of sperm-cells as those I had seen on 

 H. vulgaris in December, 1871. On placing them 

 in a shallow glass cell by themselves, 1 had the 

 pleasure of witnessing the rupture of the sperm- 

 cells as I had previously done on H. vulgaris : also 

 I noticed, June 7th, a peculiar rising or swelling on 

 the lower part of the body, quite different in appear- 

 ance from the sperm-cells, or from the appearance 

 when budding or gemmation is about taking place 

 (fig. 11). On seeing this peculiarity, 1 kept them 



Fig. U. Commencement of 

 swelling on body of Hydra. 



Fig. 12. Ditto incieased to 

 formation of ovi-sac. 



almost constantly under observation with the 

 microscope, and saw the various progressive changes 

 that took place [in the development of the ovi-sac, 

 for this it proved to be (fig. 12). The sperm-cells 

 were on the same Hydra ; the full development of the 

 ovi-sac took three days from the first appearance of 

 the swelling on the body, until its separation from 

 it as a perfect globe (fig. 15), when it sank to the 

 bottom of the glass. I was reluctantly obliged to 

 forego any further investigation, as I was away from 

 home for fifteen days ; but previously to leaving I 

 sank the glass cell with its contents in a white 

 shallow pan, under a glass shade. On my return I 

 found that the globe-shaped ovi-sacs which I had 

 seen issue from the Hydras, had disappeared, and 

 spread over the bottom of the white pan were a few 

 very minute Hydras ; indeed, so small as not to be 

 detected without a glass, a^J so transparent that. 



