946 RECORD OF CURRENT RESEARCHES RELATING TO 



branches of the alga, though occasionally a branch of the alga was 

 bitten off and added to the framework ; but very soon the animal 

 began to work bits of excrement and bits of alga into the net. In this 

 case the pellets of excrement, as passed, were taken in the gnathopods 

 and maxillipeds, and apjiarently also by the maxillae and mandibles, 

 and broken into minute fragments and worked through the web, upon 

 the outside of which they seemed to adhere, partially by the viscosity 

 of the cement threads, and partially by the tangle of threads over 

 them. Excrement and bits of alga were thus worked into the wall of 

 the tube until the whole animal was protected from view, while, during 

 the whole process, the spinning of cement over the inside of the tube 

 was kept up. 



When spinning the cement threads within the tube, the animal was 

 held in place on the ventral side by the second pair of gnathopods and 

 the caudal appendages, the latter being curved beneath the anterior 

 portion of the pleon, and on the dorsal side by the third, fourth, and 

 fifth pairs of persoopods extended and turned up over the back, with 

 the dactyli turned outward into the web. The sj)inuing was done 

 wholly with the first and second peraeopods, the tips of which were 

 touched from point to point over the inside of the skeleton tube in a 

 way that recalled strongly the movements of the hands in playing upon 

 a piano. The cement adhered at once at the points touched and spun 

 out between them in uniform delicate threads. The threads seemed 

 to harden very quickly after they were spun, and did not seem, even 

 from the first, to adhere to the animal itself. 



Development of Orchestia Montagui and 0. Mediterranea.* — 

 Herr TJljanin gives an account of his observations on the early stages 

 in the development of these " sand-fleas." 



He deals especially with the formation of the blastoderm and of 

 the germinal layers. He was unable to detect the germinal vesicle. 

 Sections showed in each of the four cleavage spheres a stellate cell ; 

 these cells jjass to the periphery gradually. They are of considerable 

 size, and consist of a granular j)rotoplasm, which gives off" more or less 

 long filamentous processes. Their nucleus is large, and there are also 

 two or three nucleoli. It is they alone which give rise to the later 

 blastoderm cells. At the time when there are, altogether, thirty-two 

 cells, the cleavage spheres begin to get indistinct boundaries, and, a little 

 later on, the limits between them disappear altogether. The smaller 

 and peripheral cells which go to form the blastoderm become closely 

 appressed, and the whole mass takes on a polygonal form. This por- 

 tion, when complete, covers over nearly two-thirds of the surface of 

 the egg, and consists of cubical, somewhat elongated cells. The 

 mesoderm commences to be developed before the ectoderm is com- 

 pletely formed. It clearly enougli owes its origin to that layer, aiising 

 close to the edge of the blastoderm disk in the form of a small rounded 

 thickening. In the course of growth it reaches to the oj^posite side of 

 the egg, or to that at which the dorsal region of the animal is, later 

 on, developed. Now is shed the so-called cuticle of the blastoderm. 



* ' Zool. Anzeig.,' iii. (1880) p. 163. 



