INVERTEBRATA, CBYPTOGAMIA, MICROSCOPY, ETC. 



695 



form, undergoes great changes during the breeding season. These 

 changes affect not only the quality and quantity of the secretion, but 

 even the form of the ultimate constituents of the gland. 



However the structure of the mature testis may diifer in different 

 fishes, that of the unripe gland is the same in all. It is made up of 

 polygonal acini, containing a rounded or slit-like lumen, so that the 

 whole gland viewed as a transparency under the Microscope, presents 

 a number of regular polygonal areas. 



In respect of the structure of the ripe testis, the Acanthopteri are 

 very sharply distinguished^ from other Teleostei. The glandular 

 substance is arranged in long, blind tubules arranged in a radiating 

 manner around a centre formed by the hilus or place of exit of the 

 vas deferens. In the remaining members of the group, the testis 

 is formed on what Brock calls the Cyprinoid type. The tubuli 

 form numerous anastomoses with one another, and so produce com- 

 municating spaces, the gland, in tyiucal specimens (Cyprinoids), 

 having a spongy appearance. This diiference in the structure of the 

 adult gland, notwithstanding the similarity of the yoimg condition in 

 the two types, is due to the fact that the increase in size of the organ, 

 during the breeding season, comes about as a result of an independent 

 increase of the elements of the gland in obedience to a fixed law, and 

 is not primarily due to a mechanical dilatation by the accumulated 

 sperm. 



The author believes that the tubules are not separated from one 

 another by interstitial tissue, and that they jiossess no true tunica 

 propria, but that they rather represent a series of lacunae (Hohl- 

 raumen), the partitions between which spring, on the one hand, from 

 the tunica projjria of the testis, while, on the other hand, they are 

 immediately continued into the partitions of the vas deferens. 



The epithelial cells of the gland are large and round, with finely 

 granular contents, a large, clear nucleus, and no demonstrable 

 membrane. The first stej? in the formation of the spermatozoa is the 

 multiplication of the nuclei, the process not taking place simul- 

 taneously in the whole acinus, but beginning with a few cells, or it 

 may be with but a single cell. By a repetition of this process the 

 original epithelium disappears, and in its place are found large cells, 

 filled with granules (Inhaltskcirperchen), which stain deeply with 

 carmine or logwood, and are probably the descendents of the original 

 nuclei. From these granules the spermatozoa are formed. After the 

 rij)ening of the latter it seems probable that the spermatic cells form 

 multinucleate masses of protoplasm, without distinct cell-boundaries, 

 that these divide into as many daughter-cells as there are nuclei, and 

 so reproduce the original epithelium. 



Female Organs. — The ovary presents great differences in the 

 arrangement of the ovigerous surfaces ; these will be best seen from 

 the following table. 



A. Ductless ovary. 



1. Ovary consisting of a simple lamina (Anguillula). 



2. Ovary consisting of numerous lamina? (Salmonidoi) 



