LIMIFOSSOR TALPOIDEUS. 71 



makes its waj' between the halves of the gonad to an opening in the septum 

 bounding the head cavity. This latter space communicates with a well-defined 

 pedal sinus, which perforates the septum and pursues its course posteriorly, 

 communicating here and there with the general visceral cavity, to the neighbor- 

 hood of the cloacal cavity. Here both sinuses unite on their way to the gills 

 from which the blood passes above the dorsal gill retractor to enter the heart. 



The brain, clearly bilobed, develops fibres which unite with five pairs of 

 precerebral ganglia that in turn give rise to nerves passing to the sensory plate. 

 The lateral, pedal, and labio-buccal connectives unite before entering the brain. 

 The last named are first to be differentiated and holding the usual position at 

 the sides of the pharynx, they unite with the ganglia lateral to the dorsal salivary 

 glands. These nerve masses are united by the usual commissure and by another 

 passing dorsal to the pharynx in the neighborhood of the salivary glands. What 

 appears to be a complete one passes ventrally into the neighborhood of the 

 subradular organ. A nerve from each ganglion passes backwai'd and probably 

 innervates a portion of the digestive tract. The lateral and pedal ganglia, 

 with the usual relations, extend to the region of the cloaca where they unite 

 to form on each side a well-defined enlargement connected by a suprarectal 

 commissure. From each swelling several nerves arise that are distributed to 

 the cloacal and body walls; while from the commissure branches are developed, 

 dorsally and ventrally, that innervate the ctenidia. 



The gonad extends from the stomach to the pericardial cavity into which 

 it opens by relatively long and slender ducts. The coelomoducts have the form 

 of simple tubes extending from the pericardium to separate exits in the cloacal 

 chamber. Their inner openings are situated in the infero-lateral angles of the 

 pericardial cavity and are guarded by high pyriform cells devoid of cilia. On 

 the other hand the succeeding portion of the canal, of very small calibre, is 

 composed of cubical elements covered with a heavy ciliated coat. This division 

 makes its way forward to the outside of the dorsal gill retractor and unites 

 abruptly with the glandular portion, which although a single tube is so con- 

 voluted that it becomes a relatively voluminous structure. Its walls are com- 

 posed of more or less cubical cells of which the cytoplasm is scant in amount 

 owing to the presence of one or two great vacaoles. The general structure 

 bears a fairly close resemblance to certain kidney tissue yet there is no positive 

 proof that it possesses an excretory function. The outer openings are on each 

 side of the anus a short distance anterior to it, and though very minute in pre- 

 served material they are nevertheless clearly defined. 



