1875.] Mr. W. Turner on the Placentation 0/ Hyrax. 151 



running from the half in the basin to the half in the beaker, and now 

 vice versa. But after the half in the beaker has been effectually poisoned 

 all motion in it completely ceases, the unpoisoned half, however, continu- 

 ing to contract independently. If the poisoned half be now irritated, by 

 nipping with the forceps or otherwise, it does not itself move, but the 

 other or unpoisoned half immediately responds to the stimulation. If S. 

 laciniata be the species of Medusa employed, this result is particularly 

 well marked, from the fact that the unpoisoned half responds to the sti- 

 mulation by performing the highly distinctive spasmodic movements 

 already described. I have also satisfied myself that curare asserts its 

 peculiar influence upon individuals of the covered-eyed Medusae. In all 

 cases overpoisoning paralyzes the excitable as well as the motor system. 

 The strength of the solution I used was 1 in 2500, and in this solution the 

 poisoned half required to soak for half an hour. 



(e) If any sized portion of a contractile strip cut from the gonocalyx 

 of A. aurita be immersed in a sea-water solution of any of the above- 

 mentioned ansesthesiating substances, the contractile waves in the poisoned 

 portion of the strip are first progressively slowed and finally blocked. 

 Upon now restoring the poisoned portion of the strip to normal sea- 

 water, the contractile waves again begin to pass, and eventually do so as 

 freely as before. 



If any of the nutrient tubes which cross such a contractile strip trans- 

 versely be injected with a solution of any of the narcotic poisons, the 

 contractile waves become blocked at the line occupied by that tube. If a 

 discharging lithocyst be similarly injected, it ceases its discharges. From 

 the effects of chloroform and weak solution of morphia, however, it recovers 

 in the course of a night. Alcohol so injected at first causes an increase 

 in the frequency and potency of the discharges, and afterwards progressive 

 torpor. In time, however, the torpidity wears away, and finally the 

 Medusid returns to its normal state. 



IV. u Note on the Placentation of Hyrax" By Willtam Turner, 

 M.B. (Lond.), Professor of Anatomy, University of Edinburgh. 

 Communicated by Prof. Huxley, Sec. R.S. Received De- 

 cember 13, 1875. 



In his ' Lectures on Comparative Anatomy,' vol. v. p. 326, Sir Everard 

 Home stated that the placenta in Hyrax capensis is annular, like that in 

 the cat ; and in vol. vi. he gave two drawings of the placenta (pis. 61 & 62), 

 in which he not only showed its zonary form, but figured, though he did 

 not describe, the sac of the allantois as equalling in length the bag of the 

 chorion. Prof. Owen, in his description of the placenta of the elephant 

 (Phil. Trans. 1857), refers to the placenta of Hyrax as similar in spongy 

 texture and vascularity to the annular placenta of the Carnivora, and 



