CLASS OF CKUSTACEA. 495 



extremely minute but very active animals, when it immediately 

 struck us that these must have been the young which the balani 

 were throwing off the day before. On placing one of these animals 

 under the microscope, we expected to find one of those mussel- 

 like animals described by Thompson ; but instead of that, it 1 ad 

 an almost exact resemblance to the young of the genus cyclops. 

 To make sure that there had been no mistake, one of the adult 

 balani was opened, when the large cavity of the mantle was found 

 to be filled with the granules which we had formerly seen ejected. 

 A few were placed in a watch-glassful of sea-water under the 

 microscope. They were quite motionless, of an ovoid shape, 

 sharper at one extremity than the other. The eye, or rather 

 what was considered to be the eye, was observed a little before 

 the middle line, and near to the superior edge. In the course of 

 a short time, a few began to make some efforts to escape. After 

 they had done so, they were found to resemble, in their external 

 appearance, the young cyclop ides alluded to above. At first, the 

 efforts to escape were feeble, but latterly they became more 

 violent ; and by means of the tail, which was suddenly and for- 

 cibly jerked upwards and downwards, the membranes which 

 contained them were burst on the abdominal surface, upon which 

 the young animal escaped. It was some time, however, before 

 the extremit ; es were completely freed. In the course of ten or 

 fifteen minutes after they had been taken from the body of the 

 mother, these young animals were all free, and the empty sacs 

 were lying amongst them. They have a striking "resemblance, in 

 their external appearance, to the larvae of the cyclops ; and if we 

 had not had the certain evidence of having seen them taken from 

 the body of the mother, we would have pronounced them young 

 cyclopides. 



* After many fruitless endeavours, we found it impossible to 

 preserve them alive for any length of time, and were, therefore, 

 disappointed in our expectations of seeing them undergo their 

 metamorphoses. We were, therefore, uncertain whether they 

 underwent a first and second metamorphosis, and changed first 

 into the mussel- like form described by Thompson, and then into 

 the parent form, or were simply metamorphosed into the parent 

 form. Seeing that this is a distinct species from that described 

 by Mr. Thompson, it is impossible to decide this question until 

 farther observations have been made. Having been fortunate 

 enough, however, in making a series of observations of the same 

 nature on the young of the balanus balanoides, which are recorded 

 above, it will now be seen that this question is already decided, 

 viz., that the balani must undergo two changes of form, or per- 

 haps more, before arriving at a state of maturitv. 



' We will now proceed to give a short description of the larva 

 of this species. 



