NEMERTEANS 135 



the basement membrane and outer fibrous layer, and is thus well re- 

 moved from the integument. Here it lies in close contact with the 

 dorsal surface of the brain, and is closely surrounded by large nerves 

 (pi. xxn, fig. 2, sn) from the dorsal ganglia. Externally it termi- 

 nates on a slight papilla in the middle of the distinct, though short, 

 lateral groove with which the side of the head is provided. The 

 epithelium of the groove is also unquestionably sensory in its nature, 

 and lies in close proximity to the brain, from which it is supplied with 

 numerous small nerves. 



The lateral sense organs, or side-organs, are situated immediately 

 behind the efferent nephridial ducts, as in other species. They are 

 rather conspicuous in life, when they appear as colorless oval spaces 

 in the midst of the lateral longitudinal black lines, and at the anterior 

 border of the fourth transverse band. They are not very extensive, 

 but possess a remarkable degree of specialization. The sensory cells 

 are less than half as high as the neighboring cells of the integument, 

 so that each of these sense organs appears as a conspicuous oval de- 

 pression exactly on the lateral margin. The cells, too, are rendered 

 still more conspicuous from the fact that the secretions situated deep 

 among the cells assume a deep blue stain with haematoxylin and 

 orange, while the integumental cells always take on more or less of the 

 orange color, and are partially obscured by the dark body pigment. 

 The relation of the sense organ to the other tissues is shown in pi. 

 xxii, fig. 3. 



The brain and lateral nerves present no striking peculiarities. 

 There are two dorso-median nerves as in several other species of the 

 genus. The upper nerve lies in the median line, just external to the 

 outer circular muscular layer, while the lower, or inner, lies directly 

 beneath the former and just outside the inner circular muscular 

 layer. 



Reproductive Organs. Sexual products are mature in August. 

 The eggs are opaque and rose-colored, and give the characteristic rose 

 coloring to the bodies of the females at this season. They develop in 

 pouches in the parenchyma above the lateral nerves, and each pouch, 

 containing from 20 to 50 or more ova, opens directly to the dor- 

 so-lateral surface of body. The oviducts are completely formed in 

 advance of the deposition of the eggs, and are in all cases lined with a 

 distinct layer of small, closely placed epithelial cells. Even before the 

 eggs are fully mature the small pouches in which the ova of the follow- 

 ing year are to develop are already established. Several ovarian 

 pouches are encountered in each transverse section. 



