106 MEMOIR VI. 



The Ova are suborbicular in form, and of a dark brown colour, 

 and in giving birth to the animal, split at one side, and so allow it 

 to escape ; at this stage the embryo appears of an orange colour, 

 and a pyriform figure, and still remains attached to the opening by 

 its narrow end, (PI. 2, f. 6, b), all its members being enveloped with- 

 in a second tunic, in which state it is buotfed up in the water above the 

 flocculi which rest upon the bottom of the vessel, and shortly makes 

 its escape from the enveloping tunic, and swims about, but with no 

 great vivacity, under the form represented. Fig. 7, viz. that of a 

 Monoculus of the Genus Amymone of MuUer ; here we have a sin- 

 gular instance of the provident care of nature for the preservation 

 of the young, well worthy the attention of the philosophic natural- 

 ist, for were they to be born at the bottom of the water, and enve- 

 loped in sediment and flocculi, scarcely any would escape that des- 

 truction, which we observe to await such as incautiously become 

 entangled in it. In this first stage of the animal's existence, it is of 

 an ovate form, with three rowers on each side, which move in con- 

 cert ; the anterior pair of rowers are the smallest, composed of three 

 joints, and terminate in three bristles, these are probably the masked 

 antennae of the perfect animal ; the second pair of rowers are the 

 largest of all, composed of three broad confluent joints, lobed and 

 fringed beneath with bristles, these, as we shall see, become the 

 horns of the perfect animal ; the third and last pair of rowers are 

 also slightly lobed beneath, and furnished with a few bristles. At 

 the end of several days, no other alteration takes place in the animal 

 than the more complete developement of its rowers, and the elon- 

 gation of its tail, which appears slightly indented at the sides : PI. 2, 

 f. 8, it is still a Monoculus, or provided with but one sessile eye. 



As its growth and evolution go on progressively, it is observed to 

 acquire a pair of sessile eyes, in addition to the original one, the great 

 rowers become remarkably larger in proportion, the body and cau- 

 dal extremity elongate, and the permanent members gradually un- 

 fold themselves, and become effective, the anterior pairs first (PI. 2, 

 f. 8) J before the whole of these are perfectly developed, the lateral 

 pair of eyes become more salient, and at length pedunculated, the 

 whole of the original rowers become immoveable, the tail bifurcates 

 at its extremity, and the animal only awaits the last change to ac- 

 quire its perfect form, or nearly such as we see (PI. 1, f. 2).. . Dur- 

 ing these progressive changes, like all the analogous Crustacea, it no 

 doubt throws off its exuvium very frequently, in order that its crus- 

 taceous covering may be suited to the change of form and size of the 

 animal, but from the large capacity of the glass-vessel in which the 

 observed specimens were kept, the flocculi with which its bottom 

 was covered, and the fondness of the animal during its latter stages 

 to perforate through these in every direction, neither the exuvia nor 

 the act of throwing them off, could be perceived, with the exception 

 of one or two of the last casts. 



With regard to the period occupied by the entire evolution of the 

 animal, it must be observed that those subjected to notice, came to 

 hand at the commencement of winter, the most unfavourable season 

 to judge of the more common length of this period, as cold weather 

 has been found to retard the progress, and \\ armth to hasten it, in 

 many of the other l^iitoRic-triu a ; tinothcr circum);tauce vvbich un- 



