Prof. H. J. Clark on Lucernaria. 25 



in question, splits off from the outer wall along two lines corre- 

 sponding to the two borders of the generative organ, and hangs 

 loosely, in ribbons, in the digestive cavity. From the newly 

 formed raw face of these ribbons the eggs or spermatic particles 

 escape into the main chamber of the disk. This I take to be 

 the universal rule, and such the type of genitalia among all 

 Steganophthalmata — a structure totally unlike that oi Lucernaria, 

 in which the inner wall alone is concerned in the highly compli- 

 cated reproductive organs. 



Passing now to the consideration of the muscular system, I 

 will call your attention to the four white slender columns which 

 alternate with the four dark tubes imbedded in the gelatini- 

 form substance of the peduncle. Sars was the first to indicate 

 the true nature of these columns, and he rightly called them 

 muscular cords. They extend from the base of the peduncle 

 to the base of the proboscis, coursing along just beneath the 

 outer wall, but still within the gelatiniform substance, until they 

 reach the upper third of the peduncle, and then, gradually ap- 

 proximating the axial line, they meet the inner wall of the disk 

 just below the base of the proboscis, and thence pass along, 

 still beneath this wall, for a short distance, aiid finally each one 

 enters the oral side of the disk at the inner or axial end of the 

 partition. At this point, each muscular column expands and 

 forms a fan-shaped layer just beneath the outer wall, and extends 

 laterally so as to occupy the whole space between the two halves 

 of a genital. At the distal end, this layer diverges right and 

 left of the partition into a broad muscular band, which borders 

 the disk and is eventually distributed in ridges or cords beneath 

 the outer wall of the tentacles and the auricles. At the inner 

 end of the partition, the muscular layer also passes into the base 

 of the proboscis, and forms a stratum immediately beneath the 

 outer wall. At four equidistant points, alternating with the 

 partitions and genitals, and opposite the four corners of the 

 proboscis, there is a weaker muscular layer, which occupies the 

 same relative position in regard to the outer walls as does the 

 stronger system of muscles first mentioned. On the one hand 

 it passes into the marginal muscular band; and on the other it 

 enters the corners of the proboscis, and forms a layer in common 

 with the one extending from the partitions. By these alternating 

 stronger and weaker divisions of the muscular layer, the disk is 

 relieved of the sameness which prevails in the muscular system 

 of the Steganophthalmata, and we have indubitable proofs of a 

 higher degree of specialization than in the latter order, where 

 the unvarying repetition of similar divisions all around the disk 

 unmistakably indicates inferiority. Moreover, in addition to 

 this, we have a peculiar specialization of the gelatiniform layer, 



