ACUALIS. 



377 



Fig. 81. 



SKlcral)le contractility, and niiglit at one time be seen thrown forward (r) towards the mouth, and at 

 another thrown back {i) so as to expose the whole of that 

 part of the hydranth-bodj which lay above them. The very 

 delicate transparent perisarc which invested the stem be- 

 came, just below the hydranth, so thin as to be with 

 difficulty detected ; here the stem w as irritable and con- 

 tractile, and the hydranth would frequently be seen to 

 incline from side to side, or would assume a nodding 

 attitude, as represented m the right hand figure (c). 

 The hydranth was of pale vermilion colour and, the 

 stem nearly colourless. No trace of a gonosome was 

 present. 



Though this little hydroid differs from Acliaradria 

 larynx in characters which may be deemed of specific 

 value, I am not disposed to assign to it the rank of a 

 distinct species. It has all the appearance of an immature 

 form, and I regard it as the young state of A. larynx. 

 Indeed the mature state of Acliaradria has probably not 

 yet been seen. 



The aquarium in which it occm'red was stocked bv o am na arym (yonng s^mmeii). 



1 -J rt, Natural size : 6, magnihed; c, hyaranth and 



Mr. Rotch from the shores of the Channel Islands. distal extremity of stem ; the hydranth has 



here assumed a droopmg posture on its stem. 



ACAULIS, St'mpson. 



Name. — From a negative, and /oauXoc, a stalk, in allusion to the supposed absence of a 



hydrocaulus. 



TROPHOSOME. — Hxdeocaultjs unknown. Hydranth sub-cylindrical; ten- 

 tacles of the proximal set long, filiform, disposed in a single verticil near the 

 proximal extremity of the hydranth ; those of the distal set, short, capitate, scattered 

 upon tlie body of the hydranth. 



GONOSOME. — GoNOPnoRES sessile, scattered, springing from the body of the 

 hydranth, between the proximal and distal sets of tentacles ; form of medusa unknown. 



Our ignorance of the form of the gonophore will not allow ns to assign the genus Acaidis 

 to any special family otherwise than provisionally, and it is only with such reservation that it is 

 here placed in the Fennaridce} 



' By au oversight Acaidis is placed under the family of Corymorphidce in page 240. 



