CHAPTER XXII 

 MALE AND FEMALE NIDAMENTAL TISSUES 



BY the nidamental tissues is meant all those animal tissues which are 

 used to secrete or form coverings of fluid or solid material in which 

 the ripe reproductive elements are to be transported or protected upon 

 leaving the gonads. Many forms show no development of such organs, 

 and the eggs and sperm are cast out at random into the surrounding 

 water. The sea urchin and starfish show an example of this condition. 

 The degree of the individual's specialization and organization does not 

 seem to affect the development of these structures, as can be noticed 

 when we recall that most of the highly organized and specialized teleost 

 fish deposit their ova and sperm much as the echinoderms do. Also 

 many low and simply organized creatures have elaborate nidamental 

 organs, as the flatworms and others. We shall, therefore, in our dis- 

 cussion, pay little attention to the systematic position of our example, 

 merely indicating the conditions under which it lives and which make 

 these structures a benefit. 



The use of fluid as a carrying body is one that greatly aids the proper 

 placing of the reproductive cells. While this is used in the discharge of 

 some eggs, it is of especial use, and a necessity to, the transportation 

 of the very small spermatozoa. 



Most eggs are carried or aided in their passage from the body by : 

 first, some sort of follicle liquor which is secreted by the cells of the 

 membrana granulosa, a region of differentiated nurse cells in the ovary 

 of man and other vertebrates ; and, second, by the general coelomic fluids 

 of the body cavity which occur in all forms in which the gonads rupture 

 into this space. 



Likewise, the spermatozoa are invariably borne in a liquid that is 

 secreted or in some way produced in the seminal lobule. This liquid 

 is reenforced in some cases by the products of certain accessory glands 

 which pour out a heavy fluid that is specially adapted in consistency 

 to carry and discharge the sperm, and is also fitted by its composition to 

 nourish and keep them in health and activity for long periods. 



The prostate gland of the mammals is a specific example of such an 

 accessory structure. Figure 449 shows a section of this gland taken 



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