8 Mr. H. J. Carter on the Conjugation of 



its alate appendages, and in the form of the endochrome, which, 

 instead of being separated into two portions united through the 

 intervention of the nucleus and its capsule, as in the navicular 

 forms, and in Naviculce generally, appears to consist of a single, 

 continuous, thin layer like that of Cocconeis Pediculus. The 

 lateral surfaces are not lanceolate {" anguste lanceolata''), as 

 Kiitzing^s description would seem to imply, and as they appear 

 to be ; for when it is remembered that they are mere margins 

 formed in the way mentioned, it is evident that this cannot be 

 the case ; but that it is the margins of the central valves which 

 present the lanceolate figure (fig. 35), more particularly in the 

 navicular forms ; while in the species under description they are 

 suddenly compressed at the extremities, and laterally present the 

 form of a bottle at each end (fig. 36) . Hence I am inclined to 

 doubt the identity of this with Kiitzing^s Amphiphora alata. 



Besides the two bright-looking tubercles (holes *) at each ex- 

 tremity of the frustule which mark the union of the lateral 

 edges with the corners of the central valves, there are two other 

 tubercles or holes, one on each side in the angle of constriction 

 (fig. 36), and therefore corresponding in position to the hole or 

 mark in the centre of the lateral surfaces of the NaviculcBf. 



Deduplication takes place through the centre of the flat 

 surfaces, and the new individuals, besides remaining together 

 until they are fully formed, sometimes separate before this takes 

 place, and then present the wing-like appendages on one side 

 only. In fig. 38, where deduplication is nearly completed, the 

 central valves respectively will as a matter of course be found to 

 be much narrower than the one represented in fig. 32, where 

 deduplication has not yet commenced. 



EXPLANATION OF PLATE I. 



N.B. The black shade in all the figures is intended to represent the 

 endoehrome. 



Fig. 1. Cocconeis Pediculus (Kg.). The two conjugating frustules rela- 

 tively magnified. The largest ttVtt of an inch long. 



Fiff. 2. Opening of the frustules and approximation of the primordial 

 utricles with their contained endochromes. (Conjectural figure.) 



Fig. 3. Union of the two utricles to form the sporangium. 



Fig. 4. Spherical form of the sporangium. 



Fig. 5. Elongation of ditto, and disappearance of the valves of the small 

 frustule. 



Hg. 6. Elliptical form of ditto, with the thin valve of the large frustule in 

 front. 



Fig. 7- Ditto, with the line of deduplication and the valves of both frus- 

 tules still adherent. 



* Kiitzing and Meneghini. t Mcneghini, I. c. p. 422. 



