1865.] Zoology and Animal Physiology. 137 



and live quite separate from the two fresh-water forms of Crustacea. 

 M. Sars considers the presence of these Crustacea in the Scandinavian 

 lakes to furnish evidence that, at the glacial epoch, the basin of the 

 Baltic was in communication with either the Eastern or Western 

 Arctic Ocean. 



M. N. Lieberkuhn, in a recent memoir upon the Spongillae, de- 

 scribes some peculiar motory phenomena not heretofore observed in the 

 Sponges. In sume species the cutaneous pores are dispersed in great 

 numbers over the whole surface of the Sponge, and usually lead into 

 a large cavity belonging to the system of ingestion. The walls of the 

 partitions bounding these cavities have vibratile apparatus. In others, 

 the body is traversed in all directions by trabecular of different thick- 

 nesses, wdrick are often supported upon the integument. Some of 

 these are completely smooth in appearance, the strongest bearing 

 vibratile apparatus. The pores of ingestion are not characteristic of 

 the integument, as perfectly similar orifices are seen to originate in 

 the membranous partitions of the interior of the body. The tubes of 

 ejection are the seat of very peculiar movements, for he has seen the 

 cells of the innermost layer gliding up the wall of the tube, and again 

 descending. M. Lieberkuhn has also demonstrated a fact which has 

 only been suspected since the observations of Laurent, viz. the repro- 

 duction of sponges by spontaneous division. In individuals kept in 

 vessels filled with spring-water he has seen the body contract, and 

 emit here and there processes which soon became detached and glided 

 over the vacant portions of the siliceous skeleton, and even upon the 

 bottom of the vessel. This division appears only to take place in 

 individuals which are nearly perishing, but the fragments set free 

 continue to live, and in the course of a few weeks they have produced 

 in their interior siliceous spicules and vibratile cilia. 



That indefatigable and excellent microscopist, Dr. Beale, has been 

 studying the structure of the sarcolemma and its relations to the 

 muscular fibre on the one hand, and to the nerve-fibre and tracheae on 

 the other. This investment, as is known, is not universally found 

 upon human striped- muscle, and while the general opinion of Conti- 

 nental anatomists is that the nerve-fibres actually perforate the sarco- 

 lemma, and come in contact with the contractible tissue, Dr. Beale 

 believes that ihis is an error arising from misinterpretation of the 

 appearances observed. With regard to insects, the sarcolemma is 

 seen delicately striated, arising not from the muscular strife, but pro- 

 duced by the ramifications of fine branches of the trachea;, which with 

 nerves may be followed in considerable number to the sarcolemma. 

 Under favourable circumstances, however, the highly elaborate ar- 

 rangement of the nerve-fibres and trachea of the muscle may be 

 observed. The fine trunk of the nerve, one of several terminating 

 ones, is compound, and consists of a number of exceedingly delicate 

 nerve-fibres, each one of these being composed of still finer fibres, 

 which subdivides very freely, forming an elaborate network, which 

 may be traced over every part of the sarcolemma. The arrangement 

 of the tracheae is equally elaborate, forming a network of extremely 



