732 SUMMARY OF CURRENT RESEARCHES RELATING TO 



so-called labium. It is pointed out that the difference in the number 

 of eyes, two or four, is due to some describers not having noticed 

 that the four eyes are in some cases so closely approximated as to 

 appear to be two. 



Revival of Tardigrades after Desiccation.* — The truth of the 

 occurrence of this phenomenon has been denied by various observers, 

 and the appearances explained by Ehrenberg as due to development 

 of fresh specimens from eggs left by the animals, which die in the 

 process. Professor Jung, however, considers that his observation of 

 the process in a single specimen of Milnesiiim proves the correctness 

 of the old opinion. The specimen was taken from a ditch, contained 

 eighteen eggs, and manifested lively movements. It was left for five 

 hours until quite dry, and all that could then be seen of it under 

 350 diam. was a brown speck under the cover-glass. A drop of water 

 was allowed to run beneath the latter. Almost immediately after it 

 had reached the remains of the Tardigrade a fine pellicle was evident, 

 surrounding the brown speck and manifesting the general outlines of 

 the body and ova. The normal wall then appeared, enclosing the 

 contents of the intestine ; the minutest details of the outer skin 

 appeared ; after twenty minutes the mouth with its fringes and tube, 

 the jaws, and the feet were fully developed. Subsequently the parts 

 connecting the jaws with the oesophagus came into view. No move- 

 ments and no development of the ova were observed in the three hours 

 occupied by these observations. The too close apposition of the cover- 

 glass to the slide being now remedied, the animal was supplied 

 plentifully with water, but, when searched for the next clay, could not 

 be found, having probably departed in search of more comfortable 

 quarters, for the algse which had surrounded it were disturbed, and 

 neither the remains of the jaws and skin usually found after specimens 

 have died, nor the eggs, were discovered. 



5. Crustacea. 



Circulatory Apparatus of Marine Hedriophthalmata.f — In this 

 elaborate essay M. Yves Delage first deals with the Isopoda and 

 Amphipoda, between the circulatory organs of which there is, he 

 says, at first no great resemblance. In the latter we see the greatest 

 simplicity, arterial ramifications are rare or absent, the blood-cavities 

 are large, the venous and arterial systems are not discrete ; in the 

 Isopods there is great complexity of arrangement, arterial ramifica- 

 tions without number, the blood-cavities are narrow or distinctly 

 limited, and the venous and arterial systems are perfectly distinct. 

 Notwithstanding these difierences the author thinks that the one set 

 may be shown to have a fundamental resemblance to the other, and to 

 be but a more perfected apparatus. 



Dealing wath the primary objection that the heart of the Am- 

 phipod is thoracic, and that of the Isopod is abdominal in position, 



* Zeitsch. Gesammt. Naturw. (Giebel) vi. (1881) pp. 190-2. 

 t Arch. Zool. Exper. et Gen., ix. (1881) pp. 1-173 (12 pis.). 



