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 fish 

 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, and 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 effects 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. « 11 



