ADHESION AND SPINNING 409 



butterflies seems to be in various sacs on the body or in various positions 

 on the wings. In these cases the hypodermal cells which formed the 

 scales or hairs also secrete a fluid which is discharged through the scale 

 in minute quantities, and vaporizes in the atmosphere. 



While many invertebrates below the insects have peculiar odors we 

 cannot discuss them as special odorous organs because enough is not 

 known about them. This is especially true of animals living in the water, 

 although it is satisfactorily proven that some forms of water animals 

 have a keen sense of smell (selachian fishes). 



Technic. These tissues are usually fairly easy to cut, and paraffin 

 section from Flemming and Zenker material show all that is to be seen 

 with the exception of the innervation and, perhaps, blood distribution. 



LITERATURE 



Rossi, G. "Le glandole odorifere dell' Julus communis," Zeits. f. wiss. Zool., Band 



LXXIV, S. 64, 1903. 

 WEBER. "Uber eine Cyanwasserstoffsaur bereitende Druse," Arch. f. mik. Anat., 



Band XXI, S. 468, 1882. 

 ZIETZSCHMANN, H. " Beit rage zur Morphologic und Histologie einiger Hautorgane der 



Cerviden," Zeits. f. wiss. Zool., Band LXXIV, S. i, 1903. 

 WILLISTON, S. A. "A Protective Secretion of Eleodes ejected from the Anal Gland," 



Psyche, Vol. IV, p. 168, 1884. 



BORGERT, H. "Die hautdrusen der Tracheaten," In. Diss., Jena, 1891. 

 VOSSELER, J. "Die Stinkdrusen der Forficuliden," Arch.f. mik. Anat., Band XXXVI, 



S. 565, 1890. 



TISSUES OF ADHESION AND SPINNING 



These structures are found in a number of lower animals where they 

 are fastened to a rock or other surface. They form a fairly homogeneous 

 group of tissues and even the organs that these tissues compose afford 

 a number of close homologies. The two principles involved in most 

 of them are the development in a columnar epithelium of two features; 

 a set of non-elastic fibrils to afford strength and points to attach, and 

 the secretion of some tough, gummy substance to cause the cells to adhere. 

 In larger forms, epithelial cells, which are usually invaginated into 

 glands, are used to secrete an adhesive fluid that can be extruded as a 

 thread which sticks and hardens. In other forms the principle of suc- 

 tion is brought into use and various suckers, pads, etc., are used to attach 

 the creature, usually temporarily, to some surface. Mechanical grasping 

 organs will not be considered here. 



The Protozoa show many forms of this power which, unfortunately, 

 cannot be properly studied on account of the weak development and 



