458 RECOED OF CURRENT RESEARCHES RELATING TO 



wliich extend from the cesophageal tube to the porus abdominalis ; in 

 externalappearance they have a close resemblance to the genital septa, 

 but they enclose a groove which extends from the upper oral angle to 

 the aboral end. 



(2) Genital Septa. — These are not so broad as the preceding, and 

 are distinguished by the presence of a well-developed ridge at their 

 free edge. The substance of these increases at the generative 

 periods. 



(3) Filamentous Septa. — Of trapezial form, with their longest side 

 inserted into the body-wall, and their shortest dependent into the 

 " body cavity " ; these bear a number of variously coiled and branched 

 filaments. The substance of the septa is excessively thin and trans- 

 parent, and they contain no specially remarkable elements. 



Coming to histological details, the author attaches some im- 

 portance to the fine network of branched processes from the ecto- 

 dermal cells, which he calls the interbasal network ; this is best 

 shown in osmium or gold chloride preparations. The fibres, which 

 are exceedingly fine, run in parallel lines, and give off at right 

 angles branches which pass either to the ectodermal cells or into the 

 mesoderm. This appears to form a nervous apparatus ; the system is 

 best developed in the upper half of the body, and here too we find a 

 large number of urticating capsules, and here the ciliary action of the 

 ectodermal cells is most energetic. So too in the tentacles, which 

 must be regarded as the most sensitive portions of the body, the inter- 

 basal network occupies a wider space than it does in the oral disk or 

 at the aboral end of the body ; where this structure becomes dimi- 

 nished the glands of the ectoderm are more completely developed. 



The sensory character of the urticating cells is spoken to by their 

 structure as well as by the protoplasmic body which encloses the urti- 

 cating capsule and the cnidocil which projects freely from the ectoderm, 

 and seems so much to resemble the sensory hairs found in other groups 

 of animals. In considering their structure, Von Heider points out that 

 the more we study the various forms under which the urticating cap- 

 sules or the cnidoblasts are developed, the more are we led to see that the 

 stinging cells, which at first had no other function than that of deve- 

 loping and shooting out projectiles, have in the course of their deve- 

 lopment become converted into organs of perception, and that in many 

 cases they have lost their primary function. This view is supported 

 by the characters of the so-called chromatophores or marginal bodies, 

 which are, primarily, a collection of cnidoblasts. Similar cases are to 

 be observed in the structures developed on the tentacles, and this being 

 so, the view that the basal processes are means of passage for nervous 

 excitations seems to be supported by the fact that processes of cells 

 are known to have this duty. Nevertheless, the author states that he 

 has not been able to discover any indications of ganglion cells, but he 

 thinks that the presence of one or several nerve-centres is not yet 

 necessary to the ActinisB. We must only expect to find the earliest or 

 primary arrangements ; and centres, such as ganglia are, are secondary 

 developments. When we touch a tentacle of a Cerianthus which is in 

 a state of contraction, that tentacle alone contracts ; the rest of the 



