440 Prof. A. Schneider on the Acfinicc and Corals. 



With regard to the muscuhiture, he has made out the fol- 

 lowing facts. Three body-layers may be distinguished — the 

 ectotheliunij the muscular layer, and the endothelium. In the 

 foot-plate and in the body-wall there are exclusively annular 

 fibres, in the septa longitudinal fibres, and in very limited 

 spots radial fibres, and in the tentacles longitudinal fibres ex- 

 ternally and annular fibres within. In a great number of 

 Actinia3 the annular fibres are aggregated beneath the i)eri- 

 stome into a strong annular muscle, which is either completely 

 imbedded in the body-wall as a di fused annular muscle, or 

 projects inwards into the chambers as a ridge, forming a^;ro- 

 minent annular muscle. The peristome possesses radial and 

 annular fibres, tlie stomachal tube an inner and an outer layer 

 of longitudinal fibres, whilst an intermediate layer of annular 

 fibres occurred only in a very limited space at the mouth. 

 The muscular layer consists of the sarcolemma, the fibrillte, 

 and an interfibrillar layer containing nuclei. The sarcolemma, 

 which forms the principal mass of the body of the Actinia, is 

 called connective tissue by KoUiker. Fundamentally these 

 designations do not contradict each other ; but the term sarco- 

 lemma must be preferred, because, on the one hand, cells 

 could only be detected in it in rare instances, and, on the other, 

 it enters most intimately into the structure of the muscles. 

 This layer is always characterized by its rapid and deep colo- 

 ration in solution of carmine ; it is either homogeneous or 

 fibrous, and frequently includes fine horny spicula. The 

 fibrillar substance consists of long prismatic or cylindrical 

 fibres. These three members of the muscular layer are va- 

 riously combined in the different Actinia?, and, indeed, in such 

 a manner that we can distinguish three grades of histological 

 development. In the lowest grade the sarcolemma is bounded 

 by a straight line on tlie side of the fibrillar layer, the fibrillar 

 prisms are placed U})on it (when seen in transverse section) 

 in a straight line ; the interfibrillar substance is in contact 

 with the ectothelium and endothelium : the linear boundary 

 between the thelial and interfibrillar layers is, indeed, always 

 rendered distinct by an accumulation of dark granules ; but it 

 is impossible to detect a limiting membrane. In the second 

 grade the boundary-line of the sarcolemma towards the fibrillar 

 layer is more or less deeply undulated ; the fibrillar prisms 

 follow this line ; and the limit of the interfibrillar layer towards 

 the thelial structures remains rectilinear. In the third grade 

 the summits of the undulations unite, and we have a sarco- 

 lemma-layer which is rectilinearly bounded towards the ecto- 

 thelium and endothelium, and encloses cylindrical muscular 

 primitive bundles consisting of a filjrillar cortical substancQ 



