OF THE ACALEPHvE OF NORTH AMERICA. 335 



The two main lateral trunks (Fig. 2, a, 6) branch oflfat right angles from the central 

 cavity, and extend horizontally for some distance sideways, ascending slightly, changing 

 their position, however, to some extent, according to the state of contraction or dis- 

 tention of the digestive cavity. Five branches arise on each side from these main trunks, 

 or rather three, as we may view them. Perhaps some observers would say four, and 

 really it is difficult not to exaggerate their connection, or to distinguish sufficiently be- 

 tween their branches. The fact is, that, before branching again, the two main trunks 

 form, at their extremity, sideways, a sort of dilatation, from which arise two lateral 

 branches extending horizontally backwards and forwards, and two close together, which 

 may therefore be taken for one, ascend in a vertical direction upwards. Thus the main 

 branches from the first trunks are either three or four, as we consider the vertical one 

 as two parallel stems or only as one ; but as the branches extending horizontally forwards 

 and backwards give out not far from their origin two others, which extend also horizon- 

 tally sideways, nearly at right angles with the former, and as all these branches origi- 

 nate so near the point where they communicate with the primitive main trunks, they 

 may all with almost equal propriety be considered as arising directly from it. And if this 

 view be taken, the main trunk may be said to have five branches, four horizontal ones, 

 and one with two parallel tubes ascending vertically. The fact is, that the termination 

 of the main trunk may contract or dilate in such a manner as to present alternately 

 these different aspects. For instance, in its most contracted state, when seen from 

 above, as in Fig. 3, there are distinctly six branches arising from the main horizontal 

 trunk, the two vertical ones appearing like very short tubes, though they are actually 

 as long as the others, because their whole length is foreshortened upon their origin, 

 while the four horizontal branches are seen for their whole extent, two and two, how- 

 ever, united by their base ; so that it may with equal propriety be said, that on the 

 whole there are only four tubes, the two horizontal ones branching soon again into two ; 

 or, in the dilated state of the main trunk, when the branches arising from it are in a state 

 of contraction, they all seem to originate from one common cavity, as represented in 

 Fig. 4. Here the four horizontal tubes really seem to arise independently of each 

 other, and the two vertical ones are brought so close together as to appear like one, 

 making altogether five branches. In another state of contraction, the two vertical ones 

 may seem united, and the two pairs of horizontal ones also, when there appear to be only 

 three branches to the main trunk ; and, unless the dilatations and contractions of these 

 curious ramifications of the stems have been watched for a long time, these differences 

 may remain unnoticed, but when fully understood, there is no contradiction in the 

 apparently conflicting statements that there seem at times to be three, at times four, at 



