THE REPRODUCTIVE ORGANS. 347 



The cells have an average diameter of 0*012 mm., the lumen of 

 the individual glands 0*1 mm. (in spirit-hardened specimens, Neu- 

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

 size, which may exist singly, grouped, 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 (x),( Neumann). 



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 



O 



these glands passes into the oviduct and surrounds the eggs 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 1), 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 muscular layer. 



c. Special muscles of the cloaca. 



(i) The J/. sphincter ani surrounds the end of the cloaca from the 

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



