78 THE VOYAGE OF H.M.S. CHALLENGER. 



come on one taeniolum, and are placed in some measure on two diverging limbs of the 

 tseniola. 



The phacelli or the longitudinal rows of the gastral filaments (PI. XX. fig. 8 ; PI. 

 XXI. figs. 14-18 ; PI. XXII. figs. 23-28) are extremely powerfully developed both in 

 PeriplujUa mirdbilis and in the following Periphema regina (PI. XXIV. fig. 1). The 

 number of filaments amounts to several thousand, and their length to 30 or even 40 mm. 

 They are apparently distributed over the whole extent of the basal and central stomach 

 that they form eight continuous longitudinal rows or " phacelli," which run divergingly 

 from the conical basal stomach. Closer inspection, however, shows that the two phacelli 

 of each pair originate as diverging limbs, from a simple interradial phacellus deep in the 

 bottom of the basal stomach. They there form a simple row of short filaments, which 

 stand freely on the interradial taeniola and project into the basal gastral cavity. This 

 simple phacellus soon divides into two limbs, which diverge only slightly at first but 

 more strongly afterwards. At the pylorus they diverge so strongly that they touch the 

 meeting limbs of the adjacent tamiola in the four perradial angles of the pylorus. They 

 then run along the margin of the gastral openings (go) nearly to the upper margin of the 

 palatine groove. Each perradial gastral opening is bordered on both sides of the 

 margin by a row of long gastral filaments, which project freely into the central gastral 

 cavity. These filaments are generally 1-2 cm. long. ; many of them, however, 3-4 cm. 

 long ; their breadth varies between £ and 1 mm., but often amounts to 1^-2 mm. 

 They are sometimes more cylindrical in shape, sometimes flattened like a ribbou, often 

 tongue-shaped at the end (PI. XXII. fig. 23 ; transverse section figs. 24, 25). The struc- 

 ture of these gastral filaments is the same as usual (fig. 26). A gelatinous supporting 

 plate (z), enclosing scattered cells, is covered with an endodermal epithelium, which con- 

 tains three kinds of cells, (1) narrow, high, cylindrical flagellate cells (fe) ; (2) flask- 

 shaped glandular cells with turbid contents, consisting partly of finely granular protoplasm, 

 partly of large, strongly-refractive corpuscles (fd) ; (3) thread-shaped epithelial muscular 

 cells containing nuclei (fm). These endodermal muscular cells, hitherto sought for in 

 vain, exist, I believe, isolated here in the large contractile and very mobile gastral fila- 

 ments (fig. 28). 



The peripheric coronal intestine (" gaster coronaris ") includes the entire peripheric 

 part of the gastrovascular system (as opposed to the axial principal intestine) and 

 occupies the whole subumbrella from the pylorus to the umbrella margin. It is divided 

 into two principal sections, which are separated by the upper or proximal margin of the 

 coronal muscle. The upper or proximal section itself fills the large coronal sinus, whilst 

 the lower or distal section forms the peripheric corona of pouches. This consists of sixteen 

 quadrangular coronal pouches, which correspond to the coronal plates of the coronal 

 muscle. Three pouches, two lateral lobe pouches, and a middle pouch passing into a 

 tentacle or a sense club, run out from the distal margin of each coronal pouch. The 



