238 DESCRIPTION OF [Polygastrica. 



Genus LXXVIII. MICROMEGA. The tube little tree 

 Animalcules. Envelope double or triple, lorica siliceous, 

 mantle gelatinous and tubular, the siliceous one prismatic, 

 similar in appearance to Navicula gracilis ; no openings or 

 transverse striae are seen, but two plates of yellowish ova, 

 and longitudinal self- division, have been observed. The 

 Navicula- shaped bodies are connected together by gelatine 

 in bundles, developed in the form of stiff little tree-like 

 clusters. 



353. MICROMEGA corniculatum. The pronged Micromega 

 has a common cartilaginous trunk, very much branched, 

 cylindrical, and more than the twelfth of an inch thick ; 

 the branches are divaricated and short, and the Navicula 

 narrow and lanceolate. Found in the Adriatic. Size of 

 Navicula, 1-1 150th. 



Appended Tribe of Bacillaria. 



Genus LXXIX. ACINETA. The rayed little tree Ani- 

 malcules. The genus Acineta is a neighbouring tribe of 

 the family Bacillaria, the members of which are distin- 

 guished by being pedicled, having a simple membranous 

 lorica, and numerous radiating, retractile, but not vibrating 

 tentaculae. In A. Lyngbyi and mystacina stomach- cells 

 have been observed, and in A. tuberosa and mystacina a 

 seminal gland. Self-division not observed. 



354. A.C IN ETA Lyngbyi. Lyngby's Acineta. Lorica sphe- 

 rical, tentacules in front, the pedicle thick ; it resembles 

 a stalked Actinophrys, while the round, radiating, pale 

 yellow-coloured head, with its thick crystal-like stalk, is 

 similar to a retracted Vorticella. Found upon Sertularia 



