No. 2.] THE OVARIAN EGG OF LIMULUS. 125 



arranged in rows along the lumen, like so many intersecting 

 bead strings. The arrangement and appearance of the com- 

 pletely empty tubes can best be observed in a half-grown 

 animal, where no eggs have yet been discharged into the 

 tubes. 



This network of tubes is suspended between the carapace 

 and the liver in a subcutaneous alveolar tissue, to be described 

 more minutely later. In the turgid condition of the ovary this 

 tissue becomes greatly flattened. The entire space between 

 the liver and carapace is occupied by the enormous mass of 

 eggs, the peritoneal tissue being reduced to a thin film. This 

 does not entirely obscure the eggs when the carapace (ca.) is 

 removed. 



2. Muscle coats. — The terminal portion of the oviduct is 

 characterized by the firmness of its wall. This is due to a 

 highly developed muscle coat (PI. XIII, Fig. 15, m.c). This 

 coat consists of an outer tunic, underneath which is a thick 

 coat of muscle fibers woven together, apparently without much 

 order, into larger bundles that intersect and cross each other, 

 leaving vacant meshes between. These meshes, however, are 

 small as compared with the muscle bundles themselves. In 

 cross section the cut end of these muscle fibers and bundles 

 show various outlines, corresponding to the various degrees of 

 obliquity in which they have been cut ; but no trace of a differ- 

 entiation into a longitudinal and circular zone is to be recog- 

 nized. Sections of the larger branches of this duct, however, 

 show a distinct, rather thin inner, circular muscle coat, outside 

 of which is a thicker zone of intersecting and dividing muscle 

 fibers, with connective tissue, -blood lacunae, blood vessels, and 

 capillaries. The outermost coat consists, for the most part, of 

 longitudinal muscle fibers, the whole forming a muscular wall 

 considerably less in thickness than that of the terminal duct. 



This same muscle coat is continued over the ovarian tubes 

 proper, but in a very loose and attenuated form (PI. XIII, 

 Fig. 15, vi.c). In both transverse and longitudinal sections 

 of the ovarian tubes the same features present themselves. 

 This is true chiefly in the mature ovary where follicles have 

 already been formed. The distinctive feature is that the fibers, 



