ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 35 



strands unite into secondary strands. They are disposed passively m 

 cell-division. It seems probable that the homogeneous basal layer of the 

 pyramidal cells is due to the horizontally disposed mitochondrial strands. 

 and becomes the connective-tissue of the cutis. It is probable that 

 some of the vertical strands become tonofibrils in the adult, which are 

 in direct connexion with the cutis. 



Chromatophores of Mullus.* — E. Ballowitz has studied the changes 

 in these pigment-cells, and finds reason to believe that the cytoplasm is 

 traversed by very numerous, very delicate, radial canaliculi with thin 

 contractile plasmic walls. The streaming of the pigment-granules is due 

 to the contraction of the protoplasm forming the walls. The pigment 

 may be concentrated in the central disk or spread out to the very 

 periphery. When the granules do not reach the periphery they exhibit 

 a remarkable " dance." 



Chromatophores of Gobies. f — E. Ballowitz continues his study of 

 the chromatophores of Gobius minutvs and 67. pictus, and gives a finely 

 illustrated account of combinations of pigment-cells that occur. There 

 are melanophores (of two types), xanthophores, erythrophores (derived 

 from xanthophores), and iridocytes. Their cytoplasm is " canalized," 

 and the pigment-granules and guanin-crystals move about according to 

 the contraction or relaxation of the plasmic walls of the canaliculi. 

 The chromatophores are generally united in organ-like complexes- — 

 black-red and stellate combinations, which are minutely described. 



" Mast "-cells of the Blood.J — Alexander Maximow distinguishes 

 two kinds of " mast "-cells, those of the tissues and those of the blood. 

 They agree in showing characteristic metachromatic basophilous granules 

 in the cytoplasm, but they are quite distinct. Those of the blood show 

 a certain specificity in different types. They represent a specialized kind 

 of granulocyte, and are never to be regarded as degenerate elements. 

 They arise from " mast "-myelocytes in the marrow, and they do not 

 multiply in the blood. 



Pecten of Bird's Eye.§ — Ebba von Husen has made a careful study 

 of the structure and development and function of the pecten. The 

 tissue is a reticular syncytium of neuroglia. There is a superficial 

 epithelium with the bases of the cells turned to the outer surface, and a 

 network of anastomosing cells with fluid in the intercellular spaces. 

 There are blood-vessels with an endothelium and a homogeneous en- 

 velope. The pigment is inside the glia-cells and their processes. The 

 fibres in the pecten are glia-fibres, not nerve-fibres. They are best 

 developed at the bridge, and end on the surface of the pecten and on 

 the vessels in knob-like thickenings, which are not sensory. The cells 

 of the bridge have papilla-like elevations on their outer surface, from 

 which fibrils of the vitreous humour take their origin. This explains 



* Arch. Mikr. Anat., lxxxiii. (1913) lte Abt., pp. 290-304 (2 pis.), 

 t Zeitschr. wiss. Zool., cvi. (1913) pp. 527-93(5 pis. and 25 figs.). 

 % Arch. Mikr. Anat., lxxxiii. (1913) lte Abt., pp. 247-89 (2 pis.). 

 § Zool. Jahrb.,xxxvi. (1913) pp. 214-70 (4 pis.). 



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