r Linnea. 587 
point where this swelling begins it is surrounded with a cluster of microscopic 
globules, which before were spread all over its surface. In half an hour the 
pear-shaped excrescence is divided into four globules ; these in a quarter of 
an hour more are subdivided into eight, and in a similar period into thirty-two, 
still remaining clustered together on the top of the egg. In another half hour 
more globules appear, decreasing in size as they increase in numbers, till at 
length, from their minuteness, the part of the egg to which they are attached 
becomes almost as smooth as when they were undeveloped. The embryo tish 
now becomes discernible in the form of a whitish semitransparent speck, which 
is the rudiment of the vertebral column. The organization of the skin then 
gradually proceeds, and the embryo increases in length, coiled round the yolk, 
till the head becomes perceptible. In forty hours from the fecundation, the 
embryo tench first gave signs of motion, and at most, twelve hours later, it had 
freed itself from the skin of the egg. The fish is then two lines in length, and 
the blood has already acquired its natural colour. For some hours after leaving 
the egg, the young fry appear stupified ; they lie on their sides and are unable to 
swim, until the swimming bladder is developed, when they immediately assume 
their proper position and their natural activity. The intestines are not fully 
developed until seven days after leaving the egg, when they begin to feed vora- 
ciously, and exclusively upon animal substances. The fry of the bleak, on the 
contrary, will only eat vegetable matter, at least during this early period of their 
existence. The temperature of the room in which these experiments were car- 
ried on, ranged from 72 to 77 Fahrenheit. The ova of the bleak are larger 
than those of the tench, and are for that reason preferable for the purposes of 
observation, besides being more easily procured. When they had reached the 
point at which the globules disappear, their vitality was no longer destroyed by 
the acid before-mentioned ; but they were then placed upon a piece of black 
cloth, or more frequently on a plate of polished silver in a glass of water, and 
the changes they underwent examined by means of a single lens. The author 
afterwards had an opportunity of watching a large shoal of Cyprinus Gobio in 
the act of spawning ; he took up three or four pebbles upon which about a dozen 
eggs were deposited, and placed them in an earthenware vessel in his room, and 
paid no farther attention to them. About eight or ten days after, he observed 
four young fish swimming about with vigour, which were so transparent as not 
to be easily seen except in a dark-coloured vessel, and he appears to have met 
with none of the difficulties in rearing fish from the ova, which Herr von Baer 
states to have so much impeded his observation. 
These numbers also contain a paper on the Spermatic Entozoa of vertebrate 
animals by Professor Wagner, arid one on those of the invertebrata, by Dr 
Siebold of Danzig. The latter author also has one on the anatomy of the As- 
terias ; and there is likewise the first part of a paper on the efTects produced by 
acetate of lead on the organism of animals (dogs and rabbits), by Dr C. G. 
Mitscherlich. 
Linnea Ein Journal fur die Botanik, u. s. w. Halle, 1835-6. 
THE most interesting papers in the latter numbers of this periodical are as 
follow : Continuation of the catalogue of Mexican plants List of South Ame- 
NO VI. Q <1 
