282 T. A. STEPIIENBON 



Aliciidae, sens, strict., have been dealt with above. There 

 remains the set of forms now to be called Phyllactidae. To 

 begin with, one suspects that names have been needlessly 

 multiplied, and the mass of forms seems to present seven good 

 genera, with some synonyms. Of these seven, one can say that 

 they exhibit the same general grade of structure as the 

 Actiniidae, but with vesicles added ; but beyond that there are 

 differences and one notes five sets of them. At least two of 

 these sets are the logical outcome along slightly different lines of 

 a further development of Actiniid forms, and may be looked upon 

 as a natural family representing a stage further than the Acti- 

 niidae. In one of these sets (P h y 1 1 a c t i s and C r a d a c t i s) 

 the acrorhagi of some Actiniid ancestor seem to have developed 

 complications so as to form a sort of ruff, while the verrucae 

 remained the same; in the other set (Cystiactis, Phy- 

 mactis) the verrucae have developed into vesicles, and some- 

 times there are acrorhagi as well. In connexion with the first 

 set, it is interesting to note that one gets, now and then, an 

 abnormal individual of Actinia equina in which some of 

 the acrorhagi have become compound, in just such a way as 

 one would expect a beginning to be made in the Phyllactis 

 direction. 



It is when we come to the other genera that the chief diffi- 

 culty arises. Thaumactis is a small, possibly a young 

 form, of uncertain affinities. Bunodeopsis is very distinct 

 and is now, thanks to Diierdon, a well-studied genus ; but it 

 is possible to think of it on the one hand as an Aliciid (sens, 

 strict.) which can develop more than six pairs of perfect 

 mesenteries, or on the other as the outcome of an Actiniid 

 which has developed along a line all its own — the 

 ancestor being, even, a pre- Actiniid Boloceroides- like form. 

 Lebrunia could well enough be derived from some Actiniid 

 or pre- Actiniid in a special way. Taking them as a whole, all 

 these forms might be derived from forms like Actiniidae or 

 pre-Actiniidae, the suggestion of Aliciid origin only coming 

 in strongly in the case of Bunodeopsis. Since we can never 

 know their exact historv, and since it seems reasonable to think 



