THE EOTTFERA OF THE SCOTTISH LOCHS. 175 



hexodonta of Bergendal, I retain the latter's specific name in the meantime. Very 

 common in bog-pools, casual in lakes ; rarely seen to feed. On one occasion when many 

 were found readily feeding, some details of the head were got (fig. 13). The corona is 

 fairly large for a pellet-maker, rather less than the collar but greater than the neck in 

 diameter. The discs stand some distance apart, and the space between is occupied by a 

 conical ligule. The ligule in Bdelloids is of very uncertain stability, often appearing as 

 a sport in species where no ligule is normally present, and is therefore an unsafe 

 specific character. All the examples of C. hexodonta examined possessed one. The 

 very long antenna is kept out when feeding. 



C. pusilla, Bryce (6). (Plate III. figs. 12a to 12c.) 



The type of this species, having a meagre case, has rarely occurred in our 

 collections. The var. textrix is frequent. This has a very bulky case, composed of 

 many concentric layers of gelatinous matter. I find two forms which make such 

 I cases, and consider them as specifically distinct. One, with a very prominent spout- 

 like lower lip, is here figured (figs. 12a to 12c). The other, in which the lower lip is 

 not at all prominent, has not been fully studied. The form figured has very prominent 

 rostral lamellse, a short, thick antenna with very long setae, and the upper lip terminat- 

 ing in the median line in a projecting ligule- like process. It readily leaves its case and 

 wanders for some time unprotected. 



C. longiceps, n. sp. (Plate III. figs. 11a to lie). 



Specific characters. — Small, with oval trunk, longitudinally plicate ; neck narrow, 

 of moderate length ; head much elongated ; corona slightly wider than the collar, upper 

 lip very extensive ; basal segment of rostrum greatly laterally compressed, terminal 

 segment fairly long, terminating when fully extended in a very low cone (the everted 

 tip) covered with short cilia and with no trace of rostral lamellse. Antenna equal to half 

 the diameter of the neck. Teeth 5/5. Food moulded into pellets. Flame-cells spindle- 

 shaped ; three pairs seen. Inhabits a firm, membranous, dirty-yellow case, to which 

 much extraneous matter adheres. 



Many Bdelloids inhabit houses of some sort for protection. In Rotifer macroceros 

 and some other species the house is little more than an untidy accumulation of debris, 

 collected by the discs in the process of feeding. Others secrete firm membranous cases 

 from the skin of the trunk, and these have a definite form determined by that of the 

 body. Others, again, adopt the cast-off shells of other animals, or joints of the limbs 

 of arthropods, or even vegetable structures. Callidina annulata, C. scarlatina, and 

 the other so-called symbiotic species adopt a ready-made shelter. Cases of definite form 

 are most commonly secreted by Callidinse of the pellet-making section — among others, 

 by C. eremita, C. angusticollis, and C. pusilla, var. textrix. To which class the present 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 7). 24 



