450 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Monotidse, led Dr. G. Plessis to complete his description of the fresh- 

 water species of the genus Monotus. 



Dr. Plessis regards Zacharias' M. relidus as specifically identical 

 with his own 31. morgiensis ( = Otomesostoma moi-giense v. Graaf). The 

 genus Monotus has a single otocyst, inclosing a single otolith, in the 

 anterior region of the body : and out of the whole genus only two 

 species are found in fresh water — M. morgiensis and M. mesopJiarynx 

 Diesing. These are monogonoporous, whilst the marine forms are 

 digonoporous. The author gives a description of the anatomy and 

 histology, together with the localities of his species. He regards the 

 otocyst as being a visual organ as well as an auditory organ, since 

 it is in very close connection with a pair of pigment-spots. The 

 otolith is fixed to the wall of the otocyst, and neither cilia nor 

 auditory hairs are present. He regards the fresh-water species as 

 relicts of a marine fauna once extending over the localities in which 

 the above species are found. 



Rotifers.* — Mr. J. E. Lord draws attention to the genus Euchlanis, 

 in which the lorica is more or less depressed, and consists of an upper 

 and lower plate, connected by a flexible membrane : the dorsal plate 

 is larger and more convex than the ventral plate. The author figures 

 four forms which he has been unable to identify. One of these he 

 believes to be E. Hornemanni, in which the lorica is ovate and has 

 four ridges along the back : the foot is furcate. A second, which may 

 be E. hipposideros, has a short foot, not projecting from the lorica, 

 while the two forks are long, but have not the bristles mentioned by 

 Pritchard. The mastax in these is brachionaean, but the trochal disc 

 is not lobed. The last species resembles E. macrura, with lobed 

 trochal disc. 



Keeping Melicerta ringens alive.f — M. F. found in a dirty 

 pond a fine colony of Melicerta ringens, which for about a week 

 appeared to thrive, but as time went on they disappeared altogether. 



He accounts for this from the fact of having taken them from a 

 pond where the water was thick, and where they could find plenty of 

 food and material for building their cases, and placed them in water, 

 which, after a time, became so clear that they could obtain nothing 

 from it for their brick-making, and he is " led to think that the search 

 for Melicerta ringens is often unsuccessful from the fact of seeking it 

 in clear ponds instead of muddy." 



Echinodermata. 



Nervous System of Echinus acutus.| — M. H. Prouho states that 

 if one suitably treats a portion of the integument which covers the 

 test of Echinus acutus with chloride of gold or citric acid, numerous 

 bluish lines connected by frequent anastomoses will become apparent ; 

 the appearance forcibly recalls that figured by Prof. Loven of the 

 peripheral nervous system of Brissopsis lyrifera. Examined under a 



* Sci.-Gossip, 1886, pp. 83-6 (7 figs.), t Scientif. Enquirer, i. (1886) p. 46. 

 % Coraptes Renclus, cii. (1886) pp. 444-6. 



