ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 733 



muscular actions which maintain the body in its desired course, and in its 

 normal orientation during the whole period of movement. There are good 

 reasons for believing that these organs also send to the cerebral ganglia true 

 sensations which inform the animal as to the movements of rotation which 

 are actively or passively effected by its own body. These sensations, as 

 well as the preceding reflex acts, may be provoked by mechanical action 

 exercised, during the movements, by the fluid or by the otoliths on the 

 nervous terminations in its walls. 



As to the interesting question, which of the two functions — auditory 

 and regulative — is the more important, the author suggests that in the 

 animals which move but little — such as the Lamellibrauchiata — the auditory 

 functions may be the more useful, while in Cephalopods and Crustacea he 

 has no doubt that the regulative is the more important. 



To the obvious objection that may be raised against this new theory — 

 the fact that there are a number of Invertebrates which move about and do 

 very well without otocysts — Prof. Delage urges that the otocysts are not 

 the only organs that are capable of performing this regulative function ; in 

 some, as e. g. Mysis, the organ of sight so well performs the function of 

 the otocysts, that the ablation of the latter is not noticed so long as sight 

 remains uninjured; and we may, therefore, suppose that in Insects the 

 absent otocysts are entirely replaced by the eye. 



If this be so, and if there is no other organ which specially replaces the 

 otocysts, we ought to prove in Insects, by the ablation of the eye, the same 

 disordered locomotion as obtains in Crustacea and Cephalopoda when the 

 otocysts are destroyed. On this point the author has made a few experi- 

 ments which appears to confirm his views, but he promises to make a more 

 extended investigation into the subject. 



Pelagic and Littoral Fauna of North German Lakes.* — Dr. 0. Zacbarias 

 has investigated the pelagic and littoral fauna of the North German lakes. 

 He found twelve species and six varieties of pelagic Entomostraca, Bosmina 

 crassicornis and Temorella lacustris being new species; the former was 

 worked out by Prof. Lilljeborg; thirty- one littoral forms and two ecto- 

 parasites are enumerated ; attention is specially directed to a completely 

 rosy-red variety of Sida crystallina ; the red pigment was in the hypodermis 

 of the carapace. 



No Hydrachnida were found in the central zone of the large lakes; 

 thirty-one species were found near the shore. 



As to the Eotatoria, attention was only given to those genera and species 

 which are constant members of the pelagic fauna, and which indicate it by 

 special characters of organization, such as the completely glassy trans- 

 parency and absence of protective colours in some species, or by the pos- 

 session of spine-like cuticular processes such as are developed in not a few 

 species of Anursea. It appears that these processes serve to support the 

 delicate animal in the water. 



The most common cilio-flagellate is Ceratium hirundinella Bergh ; 

 although Dinobrya are exceedingly common in Swiss lakes, there was no 

 indication of them in those of North Germany. 



Of Turbellaria, Bothromesostoma Essenii was observed, and a few addi- 

 tions made to Braun's observations on its structure ; the most important 

 part is the very peculiar character of the enteric epithelium in those 

 individuals which contain ripe embryos ; in them the enteric cells exhibited 

 an indication to isolation, and were only loosely held together ; the embryos 

 break through the extremely thin wall of the uterus, and make their way, 



* Zeitschr. f. Wiss. Zool., xlv. (1887) pp. 255-81 (1 pi.). 

 1887. 3 C 



