It is an interesting thing that this form of section, although in actual amount so very slight, is attended with a much more pernicious influence on the vitality of the organism than is any amount of section of the general contractile tissues. Thus, if a specimen of Tiaropsis, for example, be chosen which is swimming about with the utmost vigour, and if four equidistant radial cuts only just long enough to sever the marginal canal be made, the animal will soon begin to show symptoms of enfeeblement, and within an hour or two after the operation will probably have ceased its swimming motions altogether. The animal, however, is not actually dead; for if while lying motionless at the bottom of the vessel it be gently stimulated, it will respond with a spasm as usual, and perhaps immediately afterwards give a short and feeble bout of swimming movements. These surprisingly pernicious results are not so conspicuous in the case of Sarsia, although in this genus likewise they are sufficiently well marked to be unmistakable. I here append a table to show the comparative effects of the operation in question on different species. The cases may be regarded as very usual ones, though it often happens that a longer time after the operation must elapse before the enfeebling effects become so pronounced. --------------------+-------------+-----------+-----------+--------- | Number of | Number | Number | | contractions| during one|during five|Ultimate Name of species. | during five | minute | minutes |effects. | minutes | after | after | | before | operation.|operation. | | operation. | | | --------------------+-------------+-----------+-----------+--------- Tiaropsis diademata | 57 | 11 | 0 |Permanent ---- indicans | 148 | 23 | 0 | rest. ---- polydiademata | 102 | 18 | 0 | " ---- oligoplocama | 131 | 30 | 0 | " Sarsia tubulosa | 144 | 56 | 14 | " --------------------+-------------+-----------+-----------+---------