OF ASPLANCHNA INTERMEDIA. 9 



Gosse was perfectly right, as I can now prove with the help of 

 the jaws of Dinops longijoes {Asj)hinchna eupoda Gosse), Fig. 6. 



The jaws of A. intermedia are represented in Fig. 5, and it 

 will be seen at once that they differ from those of A. hrightwelli 

 in shape and structure. Here also there is no tooth on the inner 

 margin of the ramus, but on the outer side there is a large .strong 

 hook-shaped process for the attachment of muscles, and a little 

 higher, another smaller process in the ojDposite direction. The 

 basal part of each ramus is perforated by an oval aperture. 

 The jaws are also much larger, though the animals are smaller 

 than the other species. The secondary jaws (or the vestiges of 

 the mallei, as I would call them) are present as usual, and the 

 remainder of the structure follows that of the jaws of A. hrightwelli. 



For the purpose of comparison I here reproduce my figure of 

 the jaw\s of A. amphora, Fig. 4 (also a nearly allied species), 

 which differ again in shape and structure from both the preceding, 

 particularly in having a tooth on the inner margin of each ramus, 

 and a large hook -like process on the outer side. 



With regard to the number of flame-cells. Dr. Hudson states 

 that A. hrightivelli has a number 'varying from about ten to 

 twenty on each side. Dalrymple wrote in 1849 that it has 

 " eight, twelve, or even twenty in number," but he draws only 

 ten in his figure. My own observation is that A. hrightivelli has 

 invariably about ten flame-cells attached to a straight band, and 

 A. intermedia about twenty. I believe the number to be quite 

 constant in each species, but in counting, one or two of these very 

 minute organs may be easily overlooked if badly placed. The 

 above statements of Dr. Hudson and Dalrymple are further 

 proof to me that they had, without knowing it, different species 

 under observation at various times. 



The third mark of distinction between A. intermedia and 

 hrightwelli is the male. In A. hrightwelli the male is a humpless 

 sac, widening posteriorly and quite correctly shown in Bright- 

 well's, Dalrymple's, and Dr. Hudson's figures. In A. intermedia 

 the male (Fig. 2) has two humps projecting laterally on the sides 

 •of the body, and the dorsal and ventral posterior corners also 

 project somewhat at right angles to the lateral humps, thus 

 greatly resembling the male of A. amphora, except that it is 

 much smaller in size. The females of ^. intermedia and hrightwelli 

 ^re saccate, hum^^less, and much alike in outer appearance, while 



