Prof. H. J. Clark on Lucernaria. 23 



From the middle of the base of each of the four flat sides of 

 the quadrate proboscis, a light streak, which has the deceptive 

 appearance of a radiating canal, passes in a direct line nearly to 

 the border of the disk : this is the line along which the oral and 

 aboral floors of the disk unite, and form a solid partition, by 

 which the digestive cavity is divided into four broad chambers, 

 which communicate with one another at the inner or proximal 

 ends, about the base of the proboscis, and also at the outer or 

 distal ends, through the narrow passage between the terminus 

 of the partition and the edge of the disk. In the peduncle there 

 are four equidistant broad tubes, which merge into one cavity 

 at its base, and correspond in position to the four chambers of 

 the digestive cavity. The grouped tentacles which occupy the 

 eight corners of the disk are hollow, as likewise are the auricles, 

 and communicate openly and directly with the digestive cavity. 

 This is all that constitutes the chymiferous circulatory system of 

 Lucernaria. In Aurelia we have radiating canals at the points 

 corresponding to the partitions of Lucernaria, as well as in the 

 intermediate sections. 



In Aurelia the genitalia are four single circular organs, one 

 of each being placed opposite the flat side of the proboscis ; 

 whereas in Lucernaria each genital is a double organ, the halves 

 of which have a peculiar shape, and are situated respectively 

 one on each side of the partition, and extend along the inner 

 face of the oral floor of the disk from the base of the proboscis 

 to the extreme limits of the corners of the disk, where they 

 almost touch the bases of the tentacles. Across the proximal 

 end of each partition, triple or quadruple rows of slender digiti- 

 form bodies extend each way for a considerable distance along 

 the border of each half of a genital, thus forming the common 

 appendages of the two, and clearly indicating their unity^. Each 

 half of a genital has a peculiar form, which may be represented 

 by an inequilateral triangle whose longest side extends nearly 

 in a straight line from the inner end of the partition to the ten- 

 tacles, and the two other sides, slightly curving outwardly and 

 meeting at a very broad angle, form the rest of the outline. In 

 the adult, the longest side of the triangle is to its height as two 

 to one. This feaUu-e, alone, has a degree of speciality which 

 raises these organs in rank above all others of their kind among 

 Acalephse ; but when we examine their components, we find an 



* In the family Cleistocavpidse, as I have recently characterized it 

 (Journal Boston Nat. Hist. Soc, March 1863), the genital halves are di- 

 rectly united to each other, so as to form a continuous organ across the 

 proximal end of the partition : thus there can be no doubt that there are 

 but four genitals in LucernaricB, and not eight, as described by various 

 authors. 



