16 



G. O. SAES. 



[No. 8. 



setæ originating thence exceedingly elongate, well-nigh equalling 

 the whole carapace in length. 



The so-called shell-gland, and the several internal organs, 

 bear so close a resemblance to those parts in our 2 Northern 

 species as hardly to need a detailed description. 



As regards colour, the whole body is highly transparent, 

 almost hyaline, exhibiting in large specimens only a faint yel- 

 lowish or greenish tinge. The summer-eggs, when just depo- 

 sited in the matrix, are oblong in form, and exhibit a rather 

 vi vid yellowish yolk-mass, in the centre of which a single, very 

 small, and hyaline oil-globule lies imbedded. During the progress 

 of development, the colour of the eggs fades away, the yolk- 

 mass becoming gradually absorbed; and finally, a minute residue 

 only is found in the anterior part of the embryo. 



Observations. — The movements of the animal, as ob- 

 served in my aquaries, would seem on the whole to agree with 

 those of our indigenous species. The specific weight of the body 

 being nearly that of the water, it very often happens, that the 

 animal will keep itself for some time in about the same place, 

 with its antennæ immovably extended on either side, balancing 

 the body, so as to retain it suspended in the same position. On 

 closer examination, with the aid of a hand-leus, the branchial 

 legs are found to move during this apparent inactivity in a 

 rapid and rythmical manner, this movement serving however, as 

 is well known, merely for respiration and procuring food. If 

 the animal is disturbed or would change its place, locomotion is 

 effected by a few strong propelling strokes of the antennæ, nay 

 even one such stroke, causing it to pass through the water 

 with as many sudden jerks, mostly in different directions. These 

 movements are so rapid as to make it a matter of no little 

 difficulty to catch the animal with an ordinary dipping-tube. 

 But after a short interval, the animal invariably again assumes 

 its former quiescent position. On the whole, its movements would 

 seem to be somewhat irregular and abrupt, more so apparently 

 than are those of our Northern species. 



When placed under the microscope in a small quantity of 



