262 HYDRACHNA. 



in the vicinity. Sometimes the quantity and accumulations are wonder- 

 ful. On raising a branch of privet, which dipped amidst the water of a 

 pond, I found the leaves actually weighed down by the quantity of 

 spawn investing them. 



One of the sides of a leaf bore from sixteen to twenty patches, each 

 consisting of at least fifty ova, and both sides of others had forty or fifty 

 patches, equally exuberant. 



A twig with a few leaves was consigned to a jar of water, from 

 which at least ten thousand young were hatched by the 4th of August : 

 and next day the multitude proved infinite. All these I concluded to 

 have sprung from the species Per ox or Spinifer. 



Besides the places of usual resort, the under surface of stones sunk 

 in the water is frequently invested by thousands of ova, though it would 

 be difficult to comprehend how the parents can either reach or quit 

 their site. 



Simple inspection of such leaves, as above described, is very delu- 

 sive ; a transient view would persuade the observer that what he sees is 

 very remote from the truth. 



The aggregate production of young animals is a very interesting 

 subject, in shewing the ratio of multiplication. But no specific compu- 

 tation has determined the quantity of spawn from any single specimen 

 of the Hydrachna. Patches from individual specimens of the Ferox, 

 have consisted of four, eight, nine, twelve, eighteen ova each, respec- 

 tively. These patches are from half a line to a line or more in diame- 

 ter, alike indefinite in number, form, and contents. 



But they are always a beautiful object under the microscope. 



In general the embryo seems to attain maturity in fourteen days. 

 More are sometimes required, for here, as may be readily concluded, 

 there is also frequent irregularity. 



Patches, consisting of from twelve to fifty ova, appeared on the 

 29th and 30th of August, on the sides of a vessel containing specimens 

 of the Hydrachna cruenta Plate LXVII. figs. 1, 2. One about the eighth 

 of an inch in diameter, received some accessions subsequently, and broke 

 up about the 25th of September. Plate LXVffl. fig. 9. I then rated 



