L U C E R N A R I .E AND THEIR A L T; I K S . 49 



in counting the number of fibres which lie in the circumference of the shaft of a 

 tentacle. According- to our notes there are, at least, as many as fifty in the oldest 

 sliafts. 



99. In this connection it will not be out of place to say a word in regard to our 

 method of avoiding the main obstacle in the way of preserving the nalnral propor- 

 tions of the various parts of the organization. In the bejjinnin"- of our investi<ra- 

 tions the constant and extensive contraction of the body was a source of annoyance 

 whenever it became necessary to lay open any region with the knife. Finally we 

 discov(>red that under persistent handling tlie body lost its irritability, and after- 

 ward it struck us that if we could but avoid or lessen the shock of contact the results 

 would be not so violent. Upon this we always placed our instruments in the 

 neighborhood of the body with caution, and sometimes took the pains to let the 

 animal bring itself in contact with tlieni, as if training it to tlie presence of a foreign 

 object. Brass seemed to be particularly objectionable, even though it did not 

 actually touch the body; probably tainting the water by decomposition, or perhaps 

 by inducing electric currents in it. On the whole, well polished steel needles 

 served our purpose best, taking care to renew them as soon as rust appeared on 

 their surface. With these carefully ground down to lancet point and edge, many 

 of our sections were made with scarcely a sign of impatience on the part of the 

 animal. The slowness of the process was certainly trying, not only to the patience, 

 but also to the endurance, for the utmost steadiness of hand was indispensable to 

 success. Nor did we find that cutting with a very sluirp instrunu-nt was as irri- 

 tating as pressure with a dull one ; the sharper the blade the less the resistance, 

 and consequently a diminution in weiglit, and in the diflfusion of it. We were 

 simply applying a well-known physiological phenomenon, viz., the confused sense 

 of the contact of two closely api)roximated points upon the surface of the sensitive 

 membranes. After using the precaution to observe the exact condition of the 

 region to be operated upon, and allowing the parts to recover from whatever little 

 contraction they had been excited into, through the division of their substance by 

 the scalpel, we could proceed with the confidence that whatever distortion might 

 appear did not amount to more than the body could be supposed to assume in many 

 of its most normal attitudes. Even the high muscularity of the tentacles did not 

 prevent us from obtaining a fully expanded transverse section of the shaft, and 

 applying a very high power to it. The crushing blades of scissors were always 

 avoided if possible, although even these seemed not to disturb some parts of the 

 body — the region of the chondrophys in particular. 



100. Tlie chondmmyoplax of the tentacles {figfi. 54, 90, 91, ft') is coextensive 

 with the muscular system of these organs, and forms the next to the innermost 

 layer, lying intermediate to the gastrophragma (^ 75) on the proximal sid(! and the 

 opsomyoplax (^ 98) on the distal face. It preserves all the characteristics of the 

 foundation (^ 65-68) from which it is prolonged, and we need noo therefin-e repeat 

 them here. In a fully extended tentacle it is not much thicker than the outer wall. 

 Its depth is pretty uniform from the base to the end of the sinift, but diminishes 

 sliglitly as it enters the globose tip. There it terminates in a rounded closed ex-' 

 treniity, and contributes to swell the mass of concentric layers, all, like itself, per- 



7 April, 1877. 



