LUCERNARI.'E AND T II K 1 11 ALLIES. 63 



meant by tliis apparent clifFuseness it is a mere mimetism, while its simplicity is in 

 all probability a form of unity and concentration. There is certainly a far less 

 prevalent repetition of consimilar parts than in any of the Strohiloida. Were it 

 not, indeed, for the strong indications of a special nervous system, as evinced by the 

 highly developed optical apparatus in that order, there would be hardly anything 

 left to rank it above the Lucernarioe. 



126. Neither a circniatori/ nor a respiratory system can bo said to exist, ^er se, 

 in the Lucernaria;. The effect of these functions is produced, no doubt, at the same 

 time tliat digestion takes place. The three are mere subdivisions of the process of 

 nutrition and waste, according to modern theories of the physiology of the higher 

 animals. Oar Lucernarian stands in the same rank in regard to these subdivisions 

 that the embryo vertebrate docs, at the time when its nervous system is just dawn- 

 ing into existence, and the embryonic disk is nourished directly by the meta- 

 morphosis of the vitelline, subsidiary strata; when there are no vessels to carry 

 material to the newly forming tissue, and no allantois to spread out these vessels 

 over its surface, in closest proximity to tlie air. 



§ 17. Nervous System. 



127. The Eye-spots {figs. 26, 27, 32, 83, 0). — We are cognizant of the existence 

 of a nervous system, or rather, we sliould say, of a nervous sense, by inference rather 

 than by an actual view of anything tangible. Our deductions are drawn from two 

 sources ; the one comprises the action of the animal for a determinate end, and its 

 irritability, and the other is represented by the eye-spots. The latter is the only 

 legitimate basis upon which to found a nervous specialization, and that, even, is 

 excessively meagre. We speak of these eye-spots because they occupy a position 

 at the proximal side of the base of the anchors homologous with that in whicli a 

 more highly developed and even well defined optical apparatus is to be found in 

 other Acalephaj. In our Lucernarian it amounts to a mere accumulation of pigment, 

 in unusual quantity, in a small circle, among the interstices of the prismatic cells 

 of a specially thickened wall {fig. 83, opsop)hragma). The boss-like protuberance 

 of the wall at these spots, conjoined with the conspicuous coloring matter imbedded 

 in it down to half its depth, give it strong claims to some special functional status, 

 or to a typical representation of what finds its full development in otlier Acalephs. 

 The accumulation of pigment matter at any point concentrates light there rather 

 than any other force capable of being taken note of by a nervous centre. Neither 

 odor nor sound would be affected by it, nor does it seem possible tliat taste 

 could be seated at a point so distant from the digestive system. That it is after 

 all a mere foreshadowing, or a munetism, of a more efficient organ of vision becomes 

 strongly probable when we learn that these spots lose their distinctness, or disappear 

 altogetlier, by the time the animal measures one-half an inch across the umbella. 

 ^^'llen the latter is about one-fifth of an inch across {figs. 26, 27, 28, 83) the spots 

 have attained to their greatest definiteness, and from that period onward they 

 gradually become obliterated ; not so much, though, by fading out as by the 

 increase of pigment all around them, until they lose their distinctness for want of 

 contrast. 



