870 Transactions of the Society. 



Though this has many features in common with Tavina and 

 Teresa, particularly the foot and toes, it has important peculiarities. 

 The dorsal outline is like that of the latter, the lateral that of the 

 form.er ; but both more rough and uncouth. The skin thrown irregu- 

 larly into coarse rude folds, occurring at intervals at every part, precludes 

 any fixed form, so that the figure accurately copied has become in a few 

 minutes, though gradually, flagrantly incorrect. The front is large and 

 broadly truncate, capable of pushing out, from its lower part, great 

 membranous sacs and folds, which slowly change every moment, and the 

 use of which is inexplicable. These expansions do not appear to be 

 ciliated. The mastax and trophi are as in its congeners ; there is an ample 

 brain, which carries a cervical red eye. The whole back is ridged, 

 — tectiform, not keeled (c). 



I have observed numerous examples in sea- water from the Invergowrie 

 tide- pools. They have all been remarkably heavy and sluggish in 

 manners, little given to locomotion, wholly lacking the sprightly vivacity 

 of the kindred species. 



With one ot these specimens a curious phenomenon occurred, which 

 I cannot at all explain (see h). The animal was jerking and shaking 

 itself, as if either wishing to be free from an annoyance, or else tearing 

 some prey. Having got it somewhat turned, I saw that it carried, 

 between its bent-up foot and its much developed face, what appeared an 

 egg, of dark granular substance, as if just laid, of a pointed-oval form, 

 reminding me, in shape and spotting, of a tern's egg. Whether it was a 

 real egg, or no ; if so, whether its own ; — I could not tell. It appeared 

 uninjured ; and was firmly held for several hours, — as long as the 

 Mtjtilia lived. By-and-by the interior of the " egg " displayed many 

 clear circles (of which 1 could count about twenty), closely like the 

 nucleated embryonic vesicles often seen in the ovary ; — a fact which adds 

 to the inexplicability of the phenomenon : — for they certainly were not 

 visible at first. Another thing was remarkable. The carried " egg " had 

 sensibly become less in bulk, while it retained its perfect form and out- 

 line ; yet it had not been sucked, for the Mytilia's mouth was not, nor 

 had been, in contact with its surface. After three hours, the egg was not 

 more than one-third of its original bulk. Unfortunately no further 

 change occurred during the lapse of a night ; the next morning both the 

 animal and the egg were unaltered in appearance, and the former 

 evidently dead. The species seems unusually intolerant of captivity. 

 The abdominal viscera are generally of a rich orange-brown hue, and the 

 whole tissues are more or less sufiused with the same colour. (Fig. 21.) 

 22. Mytilia producta. Skin flexible, plicate: body slender, very 

 extensile : eye single, frontal : foot and toes nearly as in M. Teresa. 

 Length 1/100 in. Marine. 



The lorica, flexible in M. poecilops, is perhaps even more so in this 

 species, and recognizable only at the posterior extremity, where each 

 lateral plate can be traced, as, with a rounded end, it curves under the 

 trunk, to approach its fellow-plate, leaving a narrow ventral cleft. The 

 face is quite truncate, slightly oblique, not abnormally developed. When 

 "liding rapidly along a seaweed, the animal is very worm-like, the body 

 and the foot, about equal in length, forming two successive cyhnders. 



