THE KEPRODUCTIVE OKGANS. 347 



The cells have an average diameter of 0"0I2 inm., the lumen of 

 the individual g-lands O'l mm. (in spirit-hardened specimens^ Neu- 

 mann). The cells contain small rounded bodies of very varying- 

 size^ which may exist singly, g-rouped, or even arranged in rows ; 

 they swell on the addition of water. Each cell possesses^ in addition, 

 an oval^ granular, distinct nucleus. When treated with Muller^s fluid 

 many of the secretory cells have the appearances shown in Fig. 225 

 II, (1, e, f; they each possess an opening ( r),(Xeumann). 



According to Neumann the great power of absorbing water, 

 which the oviducts possess, is due to the presence of these bodies, 

 which he names ' colloid granules.^ The mucous secretion of 

 these glands passes into the oviduct and surrounds the eg*gs on 

 their passage towards the cloaca : it is due to this secretion that the 

 egg-spawn is so extremely slippery and difficult to handle. 



The inner surface of the oviducts is lined with a ciliated, columnar 

 epithelium (Fig. 225 I), containing numerous goblet-cells (I and II). 



(2) The dilated portion of the oviduct has much thinner walls 

 than the anterior, narrower portion ; the glands cease abruptly at the 

 junction of the two parts. The outer coat also contains unstriated 

 muscular fibre ; the inner surface is lined with ciliated epithelium 

 similar to that of the anterior portion. 



The lymphatics of the oviducts form a net with polygonal 

 meshes on their outer surfaces ; from this branches pass inwards in 

 the spaces between adjacent glands to the inner surface, where a 

 network with elongated meshes is formed (Langer). 



C. [The Cloaca. 



a. General description. The cloaca is a short tube lying 

 beneath the urostyle ; anteriorly it receives the openings of the 

 ureters, rectum, and bladder; and in the female the openings of 

 the oviducts, in addition : posteriorly it terminates at the anus. 



b. Minute structure. The cloaca is lined internally with a 

 mucous membrane resembling that of the rectum, e.g. a simple 

 layer of columnar epithelium, which rests on a submucous, areolar 

 layer. 



The outer walls consist of a thick superficial, longitudinal mus- 

 cular layer, and a deeper, ill-developed, transverse muscidar layer. ■ 



c. Special muscles of the cloaca. 



(i) The M. sphincter aid surrounds the end of the cloaca from the 

 anus to the tip of the urostyle. It consists of striated muscle. 



