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1. Three azo-dye-binding proteins were identified in the soluble cell supernatant fraction from livers of rats that had received 4-dimethylaminoazobenzene by intraperitoneal injection. 2. One is basic and was highly purified. It has an isoelectric point of pH8.4 in barbital-sodium chloride buffer, I0.1, an S(20,w) value of 3.5s and a molecular weight determined by Sephadex chromatography of 45000. 3. It does not have N-terminal amino acids with free alpha-amino groups. 4. Digestion with Pronase gives rise to a single azo-dye-bound peptide, which on hydrolysis is shown to contain glycine, alanine, serine, threonine, glutamic acid and aspartic acid. The amino acid that binds the azo-dye was not identified. 5. On starch-gel electrophoresis the basic protein separates into a double band, indicating microheterogeneity. 6. The other two proteins were partially purified and occur in a fraction together. They have isoelectric points near neutrality and a molecular weight as determined by Sephadex chromatography of 13800. 7. The absorption spectra in formic acid of both the basic and the low-molecular-weight proteins are similar. The azonium ion has an absorption maximum at 518mmu and another adsorbed chromogen is present with an absorption maximum at 395mmu.

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NATURE 735again, threads were seen to pass from the tips of the parapodia to the wall of the tube. The animal then retreated slowly down the tube ; the anterior end moved repeatedly from side to side through a semicircle ; and the first four to fourteen pairs of parapodia move,d in circles, each slightly out of phase with its immediate neighbours, while the setre were alternately protruded and with.drawn. These movements sufficed to make a feeding funnel from the threads secreted by the parapodial glands.The funnel when completed was attached in front to the wall of the tube and behind was almost completely blocked by the animal's peristomium. Meanwhile, most of the more distal segments of the animal undulated violently, drawing water laden with suspended particles past the animal antero-posteriorly. These undulating movements continued when the funnel was complete, and particles were thus automatically sieved out of the water current. The worm then moved forward and swallowed the feeding funnel with its entrapped particles in several gulps.The numbers of parapodia involved in the various stages of the filter-feeding process and the time taken for each step vary considerably in one worm and from worm to worm. The following figures are summaries of observations from five worms : in a tube of 3 mm. internal diameter, worms ~7 cm. in length made feeding funnels 0•5-2•5 cm. long; at 16•5-20° C. a funnel was made in 30-140 sec., water was pumped through the tube for 30-257 sec. after the funnel was completed, and a feeding funnel with its entrapped particles was swallowed in 6-16 sec.The cycles of feeding may follow rapidly one after the other with a few short breaks, or they may occur with intervals of several minutes, or irregularly, for a total period of about two hours.Feeding mechanisms similar in principle to this in N ereis diversicolor have been described for C/w!,topterus variopedatus 6 , U rechis caupo 6 and some Chironomus larvre 7 • These investigations form part of a study of the feeding habits of N ereis.

Summary.-SPF rats were exposed to the smoke from 10 cigarettes per week from the age of 10 weeks until they died. Survival, body weight, tumour incidence and histopathological appearances of the lungs were compared with those for untreated sham exposed rats. Two further groups were given a single dose of 3,4-benzyprene (BP) by intratracheal instillation. One of these was then exposed to the smoke of 10 cigaretes per week till death.Compared with untreated or sham exposed rats, exposure to smoke was associated with a significant reduction in incidence of mammary tumours.Exposure to smoke was associated with an increasing incidence of collections of macrophages laden with golden-brown pigment (GBM) and of areas of cuboidal or columnar metaplasia (CCM) or squamous metaplasia (Sq.M) of alveolar epithelium. In control rats there was virtually no GBM, a low incidence of CCM and Sq.M. Four out of 406 smoke exposed rats which came to post mortem had squamous neoplasms in the lungs, 3 having lesions of doubtful malignancy and one having a squamous carcinoma. In contrast, no squamous neoplasms were seen in 197 control rats. This difference was not statistically significant.The findings in rats given a single dose of BP were, in all the above respects, similar to those in untreated rats, except that one developed a squamous carcinoma of the lung. The effects of a single dose of BP followed by smoke exposure were in general similar to those of smoke exposure only. Three rats on this treatment regimen developed squamous cancers of the lung. None of the treatments increased the incidence of adenomata of the lungs.The results are discussed in relation to other studies of the effects of smoke exposure on rats and other species.