\[)6 UKV. T. UIDDULL ON TUB BALANUS. 



the day ( 1 4th June) I sketched several figures with pen and ink ; the 

 annexed (Figs, a and b) are a side and back view. Under a high mag- 

 nifier the skin which covers the globules (near the blunt end) has a gra- 

 nulated appearance 



On the following morning, when I examined the saucer containing 

 the animals, I was surprised to see some of the eggs (as I had supposed 

 them) moving swiftly about and swimming through the water. When 

 I had taken one out and placed it in a hollow glass under the micro- 

 scope, the rapidity of its movements was such as to prevent my examin- 

 ing it ; shortly afterwards, it was seen to move more leisurely along the 

 bottom of the glass, putting forth a sort of tongue which it fixed on the 

 glass in front of itself, and then retracted so as to draw itself forward. 

 My first thought was, this is evidently an entomostracous animal, a cy- 

 pris or something similar ; but having a small creature of that kind 

 (some species of cythera probably) under the microscope at the same 

 time, there appeared a marked difference between them, the limbs of the 

 latter being evidently much more perfect. 



In the course of the day having obtained a loan of Mr Thomson's 

 work, I was enabled to compare his figures with my own observations. 



Respecting Fig. 1 , Plate IX. which is intended to represent the natu- 

 ral size of the young animal, it must be observed that this is full twice as 

 long as it ought to be, and more than twice as broad. This remark is 

 not so unimportant as it may at first appear. The size of the young 

 Balanus, as given by Mr T., has been alleged as a strong argument 

 against the correctness of his views, because perfect animals are fre- 

 quently found much smaller. Perhaps the enlargement of a minute 

 figure in the process of copying and engraving is not uncommon, 



Fig. 2 represents an indentation at the top of the case, corresponding 

 to the cleft in the animal. This has not been observed either by Dr 

 Johnston or myself. 



The annexed figure (Fig. c) answers to Mr T.'s 3d figure. The eye 

 (Fig. 4) I did not see ; of the tail I have only seen the two long bristles, 

 which are much longer than in Mr T.'s drawing. Fig. 6 I have not 

 been able to verify, but I have no reason to judge it otherwise than cor- 

 rect. 



As yet I have not been so fortunate as to ascertain the actual change 

 of the above animal into a Balanus ; but the circumstance of their being 



