ENCHYTR^EID^E 7 



uated entirely exterior to the penial bulb and in no way connected 

 with the many glands which generally are found in the bulb. This 

 latter seems to be characteristic of the subfamily of Enchytraeinae, 

 while the former is the case in the other subfamilies so far as is known. 



As regards the structure of the penial bulb there are also some 

 great and very interesting differences. For instance, the bulb may be 

 traversed by numerous trabecula or muscular strands, in two or 

 more directions, longitudinal or fan-shaped, and circular. The for- 

 mer strands run from the body surface to the periphery of the bulb, 

 while the latter form a circular layer in the bulb. These strands sepa- 

 rate the glands found in the bulb from each other. In another type 

 of bulb there are no such strands of muscles to be found separating the 

 glands, the latter being closely packed without any intermediary muscles 

 or even connective tissue. The muscular bulb is found in Mesen- 

 chytraeinae, while the non-muscular bulb is found in Lumbricillinae. 



In several species the bulb is either insufficiently developed or of a 

 degenerated type, but even in such species there are generally some 

 characteristic features left, enabling us to assign it to its proper type. 



In Lumbricillus the bulb is surrounded by a thick muscular layer, 

 being a continuation of the body wall. This is also the character of 

 the bulb in Bryodrilus, and is probably found in all the other species 

 in the subfamily. In Enchytraeinse the muscles of the bulb are more 

 numerous, forming often a thick padding over the glands of the bulb, 

 and even penetrating between them. But there are no bands of 

 muscles connecting the body wall with the periphery of the bulb as in 

 Mesenchytraeinae. Instead of one single bulb we find in Enchytraeinae 

 a number of smaller and as regards size varying glandular cushions, 

 succeeding one another both in the longitudinal and the transverse 

 diameter of the worm. 



If we thus summarize the above facts we find that in this family 

 there exist three distinct kinds of penial bulbs, differing as regarcls 

 their finer structure. 



The Mesenchytraeid bulb is a single muscular structure, containing 

 circular muscles as well as fan-shaped muscular bands connecting the 

 body wall with the periphery of the bulb. Between the muscular 

 bands are generally found numerous penial glands which open on the 

 surface of the bulb around the penial pore. The sperm-duct penetrates 

 the bulb, opening on the center of its outer surface. 



The Enchytraeid bulb is multiple, consisting of several separate 

 cushions grouped around the penial pore. In these cushions we find 

 several sets or fascicles of glands, each fascicle opening by itself on the 



