SCIENTIFIC SUMMARY. 
565 
Salt Water Entomostraca found in Fresh Water. — The younger Saars 
has been dredging in the Norwegian lakes, and has made some very inter- 
esting discoveries. In the deepest portion of the lake he drew up some of 
the mud, and found it to his astonishment full of a small red copepode, in 
which he at once recognized the salt-water species, Harpacticus chelifer , 
described by Lilljeborg. The presence of this crustacean was so unex- 
pected, that in spite of the fresh- water forms which he had also found, he 
was obliged to satisfy himself by tasting, that the water was not brackish. 
This affords, though on a different scale, an interesting analogy to what 
has been recently observed in some of the great inland lakes of Sweden ; 
viz., that the true inhabitants of the sea can in certain circumstances 
gradually accustom themselves to live in thoroughly fresh water. Here, 
however, the agency of change has not been great, alterations of physical 
conditions operating throughout thousands of years. The time in this 
instance has been much shorter. Apparently some very high flood or 
furious storm from the west has driven the sea up on some occasion 
into the loch, which lies close to the coast. Other salt-water species 
may probably have been carried into the loch at the same time, and 
perished by degrees as the water lost its saltness, while this little 
copepode was able to survive after every trace of salt had disappeared. 
— Vide Annals of Natural History , vol. xiii., No. 77. 
New Forms of MollusJcs. — The well-known conchologist, Mr. Lovell Reeve, 
deprecates the practice, at present too common, of giving mere varieties 
of shells new names, and describing them as specific forms. He illustrates 
his objections by alluding to the way in which Dr. P. P. Carpenter 
has given a name to a mere variety, while he at the same time 
expressed his belief that it was probably only a variety of one already 
named. Mr. Reeve predicts, that should ever the soft parts of the shells 
described by Dr. P. P. Carpenter be examined, it will be found that they 
are by no means (< new forms.” — Ibid. 
Classification of the Hydroida. — A great deal of confusion of zoids with 
animals has resulted from the habit, heretofore much in vogue among 
zoologists, of giving distinct specific and generic titles to medusae. It 
would be almost as justifiable to give separate names to the flower of a 
plant and the stem which supports it. Professor Allman has come to the 
rescue, and were it not for the adoption of a very cumbrous nomenclature, 
we think his efforts would be attended with success. The basis of his views 
may be thus expressed : every hydro'id whose life-history has come fully 
before us, consists (with only a single positively proved exception) of two 
sets of zoiids. One of them is destined for the nutrition of the colony, 
and has nothing to do with true generation ; while the other is, on the 
contrary, destined for true generation, and has nothing to do with the 
nutrition of the colony. For the whole assemblage of the former the 
term trophosome has been proposed ; and for that of the latter, the expres- 
sion gonosome. Whether the gonosome remains attached to the tropho- 
some permanently, or becomes in whole or in part free, thereby attaining 
an independent existence, it is equally necessary that it should take its 
place in our diagnosis of genera and species. An adequate conception of 
the hy droid can thus only be obtained, by regarding it as the product of 
