142 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



The lateral sense organs are remarkably highly specialized and 

 provided with a special musculature. This musculature consists of 

 a dorsal and a ventral band of fibers from the longitudinal muscles. 

 These pass obliquely above and below the nerve cord respectively, 

 and are nearly as large as the nerve core itself (PI. 7, fig. 56). They 

 spread out in a fan-shaped fashion among the sensory epithelial 

 cells. 



The sense organs are situated near the posterior end of the red- 

 dish brown band seen in specimens after preservation, where they 

 are conspicuous because of their lack of color. Each sense organ is 

 situated exactly on the lateral margin of the body a short distance 

 in front of the nephi'idiopores. Tliey appear as crater-like depres- 

 sions with steep walls, and are capable of considerable independent 

 movement in life. 



The sensory cells lining the sense organ are small, slender, pro- 

 vided with long cilia, and are sharply differentiated from tlie sur- 

 rounding epithelium by their lack of those deepl3'^-staining gland 

 cells, which are elsewhere very abundant in this region of the body. 

 There are numerous other gland cells, however, of a very different 

 nature and having peculiar staining properties, being only pale blue 

 with haematoxylin and orange. The nervous supply for the sense 

 organs comes directly from the underlying lateral nerves. In the 

 region of the sense organs the outer circular muscular layer is inter- 

 rupted, so that the lateral nerves lie among oblique and longitudinal 

 muscles situated immediately beneath the sense organs. 



Meprodnctive organs. — The sexual glands develop in the small 

 amount of parenchyma above the lateral vessels, and when fully 

 matured encroach upon the longitudinal muscles in the dorsal half 

 of the body. They are scattered irregularly, although they appear 

 to lie in pairs anteriorly (PI. 5, fig. 47). When mature, they are 

 closely packed together in a single row above the lateral blood ves- 

 sel on each side, and extend quite through the longitudinal muscular 

 layer (PI. 10, figs. 63, 65). Their ducts open directly on the dorso- 

 lateral asj)ects of the body (PI. 9, fig. 59). Sexual products are 

 nearly mature in August. 



Parasites. — Two of the specimens sectioned had in the intestinal 

 canal thousands of gregarines, which were well preserved and beau- 

 tifully stained. Other, and larger parasites, in the ova showed divi- 

 sion into 16 or more oval bodies, and these may possibly represent 

 a stage in the life history of the intestinal gregarine. 



