672 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mesoderm, which never forms true mesodermal somites, arises from 

 the remainder of the meso-endodermal mass after the separation of the 

 endoderm. 



North American Grapsoids.* — Mary J. Eathhun gives a synopsis 

 of the North American Catometopous or Grapsoid crabs, which include 

 the common ocypode of the New England shores, the fiddlers with their 

 remarkable development of one claw in the male, the land crab Cardi- 

 soma guanhumi, the Pinnotheres ostreum of oysters, and the anomalous 

 Palicidae, inhabitants chiefly of warm waters or of considerable depths. 



"Variation of the Rostrum in Palaemonetes vulgaris.! — Dr. Georg 

 Duncker has investigated the number of rostral spines in 1050 shrimps, 

 and his facts lead him to the conclusion that the indices of variability 

 alone, not the coefficients of variation, are morphologically significant, 

 and the former are similar in homologous characters, but independent 

 of their mean values. 



Colour Change in Crustacea, t — Messrs. F. W. Gamble and F. W. 

 Keeble's important researches on the colour physiology of Hippolyte 

 rarians were reported here somewhat fully on the appearance of their 

 paper in abstract ; in the complete memoir which is now available the 

 following points merit further notice : — First, the series of water- 

 colour drawings which illustrate the paper, and show admirably the 

 skill which the prawns — especially the females — display in selecting 

 weeds of tints which harmonise with their own, when freedom of choice 

 is allowed. Second, a detailed account is given of a relatively simple 

 apparatus in which the prawns may be readily kept alive for purposes 

 of experiment. The complete paper further contains full details of the 

 experiments upon which the conclusions stated in the abstract were 

 based, with tables of the observations. The most important point in 

 an impressive paper is perhaps the occurrence of a periodic cycle of 

 colour change — a point dealt with in the previous abstract, but the 

 paper raises many important questions in reference to the colour 

 physiology of Crustacea, some of which the authors hope to pursue 

 further. 



Annulata. 



An Atlantic " Palolo."§— Mr. A. G. Mayer under this title describes 

 Staurocephalus gregarious sp. n., a Nereid whose swarming habits he 

 has studied at Loggerhead Key, Tortugas Islands, Florida. It would 

 appear that the swarming occurs on the day preceding the day of the 

 last quarter of the June-July moon (two observations). Swarming 

 begins before sunrise, and the discharge of the genital products occurs 

 about sunrise. There is no external difference between the anterior 

 barren segments and the posterior fertile ones, but the discharge of the 

 products is so violent as usually to tear and injure the fertile segments. 

 The entire worm appears at the surface, and, shortly after the discharge 

 of the products, sinks again to the bottom, but whether the injured 

 segments are sloughed off or not was not ascertained. The eggs con- 



* Amer. Nat., xxxiv. (1900) pp. 583-92 (15 figs.), 

 t Tom. cit., pp. 621-33 (3 pis.). 



j Quart. Jouin. Micr. Sci., xliii. (1900) pp. 589-698 (5 pis.). Of. this Journal, 

 ante, p. 202. § Bull. Mus. Comp. Zool., xxxvi. (1900) pp. 1-14 (3 pis.). 



