INVERTEBKATA, CRTPTOGAMIA, MICROSCOPY, ETC. 283 



published a preliminary account,* some of them interesting as being 

 compound hypotricbous and holotricbous forms. 



1. Stichotricha socialis, n. sp. (Figs. 1-3). — This is a compound 

 hypotricbous species, found in an aquarium at the Zoological Institute, 

 Vienna. 



It occurs in the form of a soft, brownish, tree-like, dichotomously 

 branched tube (Figs. 1 and 3), springing from a single stem, and 

 with each branch open distally and containing a single infusor. The 

 latter are in constant motion, sometimes projecting a long way out of 

 their tubes, sometimes retreating far into them. If disturbed they 

 often leave the tube altogether and swim free in the water, and 

 in this case never return to their former habitation. A free form may, 

 however, start a new stock by throwing out a secretion which gradually 

 hardens in the water to the characteristic tube. The constant move- 

 ments of the animal keep the lumen of the tube sufficiently wide. 

 After the formation of the tube has gone on for a time, the animal 

 divides transversely; the two individuals thus formed take up a position 

 side by side at the mouth of the tube, proportionally widening it. A 

 septum is then secreted between the two, so that each comes to lie in 

 its own tube, and thus the first branching is brought about. 



The animal itself is elongated (Fig. 2), produced at one end into a 

 long neck, and has two widely separated nuclei (ji), each with its 

 nucleolus, and a single contractile vesicle (cv). The cilia fall into 

 three sets ; there are four spirally arranged bands of locomotive cilia 

 around the body (A, B, C, D) ; a row of cilia to the right of the long 



but really composed of fine cilia ; A, B, C, D, the four rows of locomotive cilia ; 

 n, nucleus ; cv, contractile vesicle. 



Fig. 3. — Ditto. A large colony hanging from the surface of the water. 

 Natural size. 



Fig. 4. — Tillina magna. The animal from the right side, v, anterior end ; 

 H, posterior end ; rp, ectosarc ; at H is the projection in which the contractile 

 vesicle cv lies ; o, mouth ; .^ gullet ; particles not required for food penetrate as far 

 as X, and are then driven out again; n, nucleus; p, probably accumulations of 

 parasitic bacteria ; nv, food vacuole. 



Fig. 5. — Maryna socialis. A colony of four individuals, x 90. 



Fig. 6. — Ditto. The animal seen from the ventral side, k, the cup or body 

 proper with its fine investment of cilia, tlie fissure in its margin being turned 

 towards the observer ; tr, the funnel, projecting from the cup, iind bearing long 

 cilia round its fore-cdgo ; A>, dark granules, probably giving rise to the secretion 

 for the case ; s, gullet ; cv, contractile vesicle. 



Fig. 7. — Oxijtricha tubicola. A single tube with the contained animal, x 300. 



Fig. 8. — Cothumia socialis. A colony, x 90. A, the oldest and consequently 

 darkest individual ; B-E progressively younger and therefore lighter animals. 



Fig. 9. — Ditto. The animal seen from the side, pd, disc ; p, peristome ; 

 L, lip; M, prre-oral membrane; o;*, operculum ; r, gullet; ci\ contractile vesicle. 



Fig. 10. — C. upcrcdata. The animal in .such a position that the open oper- 

 culum is seen from l)chind. op, the lino alon^^ whicii the operculum is attached 

 to the lorica ; I, tiic places where the retracting membrane rt is attached. 



Fig. 11. — Ditto. Diagrammatic representtvtion of the closing apparatus, 

 c, the Hninial ; op, the operculum : rt, retracting nuinbranc. 



Fig. 12. — Ditto. Distal end of the animal, showing the membrano IM, sur- 

 rounding the mouth o. 



Fig. 13. — TilHiux nuKjna. Encysted form, divided into four. 



* This Journal, ii. (1879) p. 899. 



