4 ENGLAND TO RIO DE JANEIRO CHAP. I 
animal, by the help of which they swim with some degree 
of activity when separated from each other. Several sorts 
are most generally seen joined together, gemma more par- 
ticularly, which adhere in irregularly-shaped clusters of some 
hundreds ; in the midst of these were generally found a few 
specimens of cornuta, from which circumstance we may 
judge that they are very nearly allied. It seems singular 
that no naturalist should have taken notice of these animals, 
as they abound so much where the ship now is, not twenty 
leagues from the coast of Spain. From hence, however, 
great hopes may be formed that the inhabitants of the deep 
have been but little examined, and as Dr. Solander and my- 
self will have probably greater opportunity in the course of 
this voyage than any one before us, it is a very encouraging 
circumstance that so large a field of natural history has 
remained almost untrod until now, and that we may be 
able from this circumstance alone (almost unthought of 
when we embarked in the undertaking) to add considerable 
lights to the science which we so eagerly pursue. 
This evening a large quantity of Carciniwm opalinum, 
which may be called the opal insect, came under the ship’s 
stern, making the very sea appear of uncommon beauty, their 
colours appearing with vast brightness even at the depth of 
two or three fathoms, though they are not more than three 
lines long and one broad. 
7th. On examining the Dagyse which were taken yester- 
day several small animals were found lodged in the hollow 
parts of their bodies, and some in the very substance of 
their flesh, which seems to be their food, as many of the 
Dagysce were full of scars, which had undoubtedly been the 
lodgment of these animals some time before. Upon a 
minute inspection they proved to be animals not to be 
classed under Linnzus’s genera, though nearly related to 
Oniscus, from which circumstance the name of Onidium 
was given to the new genus, and to them was added an 
animal taken on the 28th of August, and mentioned by 
the name of Oniscus macrophthalmus. 
In one particular these insects differ from any hitherto 
