HYDROIDS FROM WOOD's HOLL, MASS. 853 



is primitive. In the first case it would have been preceded by 

 a fixed condition of the polyp. Then the polyp by some 

 process of fission managed to sever itself from a part of its 

 foot end, and attaching itself again went through the same 

 process until fixation was entirely dispensed with, and thus 

 reverted to the ancestral free form.^ This is, however, with- 

 out parallel, unless the case of Coryraorpha furnish one. 

 One other consideration seems to outweigh the above, viz. 

 that the peculiar mode of asexual reproduction in Hypolytus 

 involves fission of the free end of the parent. It seems to 

 me, then, that it is a phylogenetic character. 



Summing up the characters of Hypolytus peregrinus, 

 we have — a single unbranched polyp of the Tubularian type, 

 with two circles of tentacles, ten in the upper and fourteen in 

 the lower ; a primitive perisarc enveloping the hydrocaulus, at 

 whose free end buds are given off by spontaneous fission, and 

 these in turn develop into polyps like the parent directly ; 

 sexual reproduction by means of ova and spermatozoa, 

 developed in gonophores situated just above the aboral circle 

 of tentacles ; on account of its unattached condition it is free 

 to move from place to place, which it does slowly. These and 

 some minor ones are characters that will have bearing on the 

 ultimate classification of our animal, which is not attempted in 

 this report. It is intended to bring out only those characters 

 that have to do with phylogeny and some other problems, such 

 as fission and budding. 



Detroit, Michigan ; March, 1898. 



' la this case we might expect the progeny to form at least a temporary 

 hydrorhiza, which, iiowever, does not talce place here as it does in Cory- 

 mor|)ha. It may be that the embryology of Hypolytus may furnish some 

 further evidence on this point. Another way of looking at the same question 

 is, that Hypolytus was an attached colonial form, in which spontaneous fission 

 took place first just below and then above a lateral bud, and this becoming 

 permanent the lateral thickenings on the blastolytes are to be interpreted as 

 the last remains of budding. 



