tW: Clark — Origin of Crinoidal Muscular Articulations. 



the dorsal ligament would contract to the farthest limit, and 

 the fibers in the syzygies, through sympathetic action, would 

 also contract, but, being normally under more or less tension, 

 would not be able to take up this contraction within them- 

 selves, but would be pulled apart, thus breaking off the arm at 

 the syzygy. Fracture of the arms at the syzygies, then, would 

 appear to be an entirely involuntary act on the part of the cri- 

 noid, due solely to the physiological effects of panic ; this 

 panic may, of course, be more or less general, or localized, so 

 that stimulus of the calyx would induce fracture at the first 

 brachial syzygy, stimulus on the arms at the neighboring 

 syzygies. 



During the growth of most of the oligophreate comatulids 

 the ten original arms are cast off, often at the first syzygy, and 

 from the stumps axillaries arise bearing several arms. Minckert 

 supposed that this was a voluntary action ; but it is noticeable 

 that all the comatulids which have more than ten arms have 

 short brachials which are correlated with a corresponding 

 shortness in the muscle fibers and dorsal ligament fibers unit- 

 ing them. JSTow it seems probable that during growth the 

 dorsal ligament fibers are able to accommodate themselves 

 gradually to their decreasing length through their contractile 

 power ; but this would have exactly the same effect upon the 

 syzygies as panic — they would be torn apart — so that the cast- 

 ing off of the arms of the ten armed young of the oligophreate 

 comatulids appears to be, not a voluntary action, but a direct 

 result of the gradual change from the juvenile to the adult 

 type of brachial. 



