16 GEAF ZU SOLMS-LAUBACH— MOIS'OGEAPH OF THE ACETABULAEIE^. 



manifest tbat in this process the cuticuloid lamella as well as the inner layer must be 

 separated by a circular cut. The transverse lamella, bordering the margin of the lid, 

 less altered than the cuticuloid layer, must then serve as a sliding surface at the 

 removal of the lid, but whether it remains with the lid or with the spore I must leave 

 undecided. 



Disregarding the great structural differences that exist between the series of Cymo- 

 poliecB, Bornetellece, and Acetabulariece, the systematic connection of these groups has 

 so impressed recent authors that they either unite them all as Dasycladece, or they divide 

 them into two allied families of Basycladece, which in this case also includes the Boi^- 

 netellecB and separates off the Acetabular iem. The more our knowledge of all these genera 

 increases the more clearly manifest becomes their connection — their morphological 

 homology. In spite of this, the literature contains only a few attempts at a careful 

 comparative treatment of their organs. Only in Ealkenberg, in Wille, and in Cramer do 

 I find observations of the kind. They carry out quite correctly the comparison of the 

 main axis — the stem, as well as the verticillate lateral members borne by it — the leaves, 

 which are distinguished by limited duration of growth and become the bearers of the 

 fructiti cation. These leaves are either all alike or they are of two sorts, partly sterile and 

 hair-like, frequently di-polychotomously branched, and partly fertile and club-shaped. 

 Ealkenberg goes farther than Wille, since he says (p. 270) of Acetahularia : — " The cell- 

 branches which unite to form the cap are distinguished from the other verticillate branches 

 not only by the absence of further branching and by their persistence on the axis, but 

 by the fact that in them only does the formation of reproductive cells take place, while 

 the hair-branches, like the chambers of the rudimentary cap, remain sterile." This 

 rudimentary cap is our corona inferior. That follows from the passage which says : — '*So 

 the cap is doubtless to be regarded as equivalent to the previously formed hair-whorl of 

 the shoot of AcetahUa?'ia ; the transition from this hair- whorl to the mature cap-whorl is 

 facilitated by a branch -whorl which remains rudimentary and surrounds the cap as a 

 cushion on its under side .... Ordinarily the capacity for forming caps is extinguished 

 with the development of the first fully-formed one. Above it, however, there are formed 

 several whorls of umbellate hair-branches, which soon fall off ; but the internodes of the 

 main axis do not extend above the cap, and the membrane of the main axis, in which 

 they were inserted, showing the scars of the fallen branches, surrounds the navel-shaped 

 depressed apex of the shoot in the form of a circular wall." According to this view 

 the cap is a highly complicated aggregation of hair-whorls placed together, of which one 

 goes to the corona inferior, another to the sporangial rays, and several to the corona 

 superior. Falkenberg has examined only Acetahularia mediterra/nea, and it in a mature 

 state; otherwise he must have convinced himself of the untenability of his opinion. The 

 position of the hair-scars in all Folyphysa^, particularly in Acetabularia polyjjhysoides and 

 A. Mobil, where they form a whorl on each side of the coronal prominences (Plate IV. 

 figs. 2, 6), shows that we have to deal in it simply with the parts of a complete peculiar 

 body — the coronal prominences. To this is to be added the late appearance of the 

 sporangial rays in the development of the cap of J. meditert^anea^ in which an originally 

 undifferentiated primordium breaks up into corona superior and an under portion which, 



