NOTES AND MEMORANDA, 297 



points out how closely they resemble in form the siliceous spicules of 

 various Sponges. He has observed how greatly these are in the power 

 of the small spiders that live with them, and which are able to para- 

 lyze their action although not able to destroy them. 



Parthenogenesis in Bees. — MM. Perez and Sanson have each an 

 article in the last number of the ' Annales des Sciences Naturelles ' 

 (Zool.),* in which they repeat and confirm the views already expressed 

 on this subject. See p. 88 of this Journal. 



Spinning Glands of the Silkworm. — Each of the two spinning 

 glands Professor Lidth de Jeude describes f as consisting of three 

 parts ; a thin-walled efferent duct, a thick and slightly coiled reservoir, 

 and a long and greatly coiled hinder pjrtion. In all three it is pos- 

 sible to make out a thin and homogeneous membrana propria, and a 

 unicellular layer of pavement-epithelium ; at the commencement of 

 the median portion of the glandular region there is also a firm cuti- 

 cular intima. The tunica projpria is traversed by tracheal ramules in 

 the median and hinder portion of the gland, and numerous branches 

 of these pass into and between the epithelial cells ; each of these cells 

 contains several twigs. The cells of the glandular epithelium differ 

 in character in each of the three regions, but they all agree in dis- 

 playing the absence of a distinct membrane, the presence of large 

 stellate nuclei, and a colourless protojilasm. The largest and flattest 

 cells are found in the median, and the smallest in the anterior part. 



With regard to the efferent duct, it is noted that the protoplasm of 

 its cells consists of closely approximated doubly-refracting fibrillte set 

 in a singly refracting substance ; they are placed at right angles to 

 the axis of the canal and give the micro-chemical reactions of albumen. 

 The protoplasm is separated from the intima by a transparent, singly 

 refracting layer, which is traversed by pore-canals ; this layer is 

 easily broken up by treatment with alkaline reagents. 



The intima, which is about y^® q ^™* thick, is of a yellowish-brown 

 colour, is very firm, elastic, and doubly refracting ; it is fibrous in 

 structure, but the fibres are not destroyed by alkalies. The lumen of 

 the efferent duct is filled by a colourless fluid, and the filaments found 

 in it are highly refracting and are anisotropic. The protoplasm of 

 the cells of the median portion is finely granular, and is not aniso- 

 tropic ; it differs in character in different regions ; the fibres which 

 are found at the periphery of the tube are also essentially protoplasmic 

 in character, and are not chitinized. The very wide portion of the 

 median region is in the posterior portion completely filled by the highly 

 refractive and viscid secretion which is found in it, and which goes to 

 form the silk-threads. 



The cellular protoplasm of the hinder portion of the gland is 

 granular, and consists of irregularly prismatic bodies; the cell- 

 substance is, when dried, highly refractive. 



The following are the more important physiological results re- 

 corded by the author : When living glands were electrically irritated, 



* Vol. vii. (1879). t 'Zool. Anzeiger,' i. (1878) 100. 



