, LARVA OF TENDRA. 21 



difficulty of investigating this point, we are unable as yet to accept 

 with certainty the interpretation that these fibrous strands are nerves. 



b. Larva of Tendra. 



If we leave out of account Cyphonautes, to which reference will 

 shortly be made, REPIACHOFF (No. 32) deserves the credit of having 

 been the first to prove the existence of a well-developed alimentary 

 canal in a typical Ectoproctous larva. This author found in the 

 larva of Tendra (^fembranipora) zostericola, which in other respects 

 follows the type of the ordinary Escharina larva, and also resembles 

 the Alcyonidium larva, an intestinal canal, the oral aperture of which 

 lies in front of the sucker, while the anal aperture lies behind that 

 organ. The Tendra larva would thus approximate to the larva of 

 Alcyojiidium in the topography of its internal organs. 



c. Larva of Membranipora and Flustrella. 



The larva of Membranipora has frequently been investigated. 

 EHRENBERG placed it under the name of Cyphonautes among the 

 Rotatoria; later, JOH. MULLER compared it with the larva of 

 Mitraria; and SEMPER, LEYDIG, and CLAPAREDE (No. 1) declared it 

 to be a Lamellibranchiate larva, SCHNEIDER (No. 5) being the first to 

 establish its true affinities as the young of Membranipora. Later 

 observations were made by ALLMAN, METSCHNIKOFF (No. 19), 

 HATSCHEK (No. 2), BARROIS (No. 6), REPIACHOFF (No. 4), and 

 PROUHO (No. 28) as to the structure of Cyphonautes, while its 

 attachment and transformation were investigated by both SCHNEIDER 

 and OSTROUMOFF (No. 3). It appears from the statements made by 

 these authors that Cyphonautes agrees closely in all important points 

 with the typical Ectoproctous larva (e.g., Alcyonidium larva), the 

 apparent differences between them being of an unessential kind. 



Cyphonautes (Fig. 8.) resembles in shape a laterally compressed 

 bell. The lower surface is bordered by cilia. If we compare this with 

 the corona of the Alcyonidium larva, we find that we must regard 

 the external surface of the bell as the aboral side, and the under 

 surface of the bell as the oral side partly invaginated to form a 

 vestibule or atrium. The whole body is covered externally by two 

 triangular shell-valves connected together along their anterior edges, 

 which run parallel to the fibrous strand (Fig. 8, /). The two 

 valves that come into contact along this hinge-line cover the laterally 

 compressed body on the two sides. Their posterior edges, which run 

 parallel to the mid-gut and the hind-gut (the intestinal edges), are 



