NIDAMENTAL TISSUES 



479 



con. 



from man. This section shows a compound alveolo-tubular gland with 



a simple columnar secreting epithelium. The cells of this layer are clear 



and secrete continu- 



ously without a 



degeneration and re- 



newal of their cyto- 



plasm. The secretion 



is not plainly visible 



at any stage of its 



elaboration, and no 



trophospongia have 



been described. The 



nucleus is round and 



placed close to the 



proximal end. Many 



concretions are found 



in the lumen of this 



gland. 



Another form of 

 male-carrying 



is Secreted by the Sper- ne li sec., coagulated secretion. (After LEWIS, in " Stohr's 



matophoral glands of Text - book f Histolo ^"> 



certain crustaceans, as the lobster and the crayfish. This fluid is 

 secreted by the walls of the sperm ducts (Fig. 450), and it not only 

 serves as a vehicle to carry the mass of sperm out of the male organs, 

 but it also forms a semifluid covering around them and attaches 

 itself to a receiving plate on the female body and hardens, preserving 



the life of the spermatozoa for 

 months or even years until they are 

 needed to fertilize the eggs. When 

 this time comes, the female surface 

 secretes a fluid which softens the hard- 

 ened sperm fluid and brings the dor- 

 mant spermatozoa back to activity. 

 Such a package is known as a sper- 

 matotheca. 



Other Carrying fluids f Of the SpCf- 



ntus.f. 



a ., FIG. 449. Part of several acini of the human prostate gland. 

 fluid cow., concretion; mus.f., smooth muscle fibers; bl., blood chan- 



FIG. 450. Transection of the seminal 



-* to be found in many 

 sticky, spermathecal covering for the other animal forms. A step in the 

 toicK.) spermat z a ' (After H " organization of this apparatus may be 

 seen in the salamander, the male of 



which secretes a covering for the sperm. This takes place in the 

 thickened folds of integument which border upon the cloacal open- 



