252 PROFESSOR PANCERT. 



tween the moment of the application of the excitement and 

 the commencement of the current, I measured it, and found 

 it l^ths of a second. 



In certain cases the ascending current takes less time, 

 and in others more ; in one case it took 4". The duration 

 of the partial currents of each branch could not be esti- 

 mated ; it is, nevertheless, much shorter than ^th of a 

 second ; the figures obtained for the descending current, and 

 for the currents of the zooids, differ in no wise from those 

 already cited. The extent of the Pennatula being, on the 

 average, 6' 1" long, and the luminous current taking 

 about 2" to traverse it, one may presume that the same 

 current would take 20" to traverse one yard ; one may also 

 suppose that, if it had to traverse the 30 metres, which the 

 motor-excitation of the nerves of the frog traverses, according 

 to Helmholtz, in 1", the luminous currents of the Pennatula 

 would take 600", or 10', to go the same distance ; it would 

 take 660", or 11', to traverse the 33 metres which the sen- 

 sation of the nerves of man and of mice traverses in 1". In 

 any case, the velocity of propagation of the excitation in the 

 Pennatulidffi is 160 times less than that which was observed 

 by Schiff in the nerves of inebriated cats, in which the 

 :^ransmissibility had been reduced to 8 metres per second. 



In this limited space I leave aside in this summary 

 considerations and comparisons* I cannot, notwithstanding 

 abstain from calling the attention of physiologists to the 

 singular properties of the Pennatulae, of rendering visible by 

 the light of their polyps the direction and velocity of propaga- 

 tion of excitation, as if in these animals the interior mole- 

 cular movement, which is produced in consequence of the 

 excitation, placed the content of the cells of the luminous 

 cords in a state which allows it to combine with oxygen — a 

 chemical action, accompanied rvith development of light rather 

 than heat. 



These ascertained facts inspire the desire to know if the 

 Pennatulidaj really have nerves. Having mentioned the 

 observations of Kolliker, as well as my own, about the 

 pale, thin, and transparent fibres seen in the little cells and 

 in the muscles of the polyps, I must, notwithstanding, 

 admit that the field remains largely open to ulterior obser- 

 vations, which ought to be made on polyps in general. 

 It appears to me that, if the nervous system is existing in 

 the Pennatvilse, it ought probably to be social, like that which 

 has been observed in some Bryozoa — for example, in the 

 Cerialariae. If, on the contrary, the above-mentioned fibres 

 were not nervous, the Pennatulae ought to enter, and with 



