TRANSACTIONS OF SECTION D. — DEPT. ZOOLOGY AND BOTANY. 373 



or Fissiparous development. Thus 0. F. Miiller describes two kinds of budding in 

 the freshwater Nats proboscidea,&nd gives an account of the same process in Nereis pro- 

 lifera (the Autolytus prolifera of modern authors). Amongst others, De Quatrefages 

 and Frey and Leuckart in the same species, Milne Edwards in Myrianida, Sars and 

 Huxley in Filigrana, 0. Schmidt in Nais, Microstoma, and Filigrana, Max Schultze, 

 R. Leuckart, and Tauber in the former species, Alex. Agassiz in Autolytus cornutus, 

 Schmarda in Catenula, and Lankester in Chcetogaster, show how widely this mode 

 of development has been recognised. The feature that mainly concerns us at 

 present in regard to these descriptions is the fact that a new animal is produced, in 

 a Hue with the old, by various modifications of budding. In no instance is there 

 any approach to a branched condition by lateral offshoots from either parent-stock 

 or bud. As an example of one of the best-known marine forms the account of 

 Autolytus cornutus by Alex. Agassiz may be cited. This species exhibits a kind of 

 alternation of generation, the parent-stock (which is a sexual) giving rise posteriorly 

 to male and female buds, which differ much in appearance from each other. The 

 latter produce ova, which by and by develop, in the peculiar body sac, into a swarm 

 of parent-stocks with which the cycle commenced. 



The discovery of a species (Syllis ramosa) of the same family (Syllida) which 

 forms an intricate series of branches by lateral budding of the parent-stock, by Sir 

 'Wyville Thomson in a Hexactinellid sponge from Zebu, is one of the remarkable 

 additions to our knowledge made by the voyage of H.M.S. ' Challenger.' 



The Syllidian 1 is located for the most part in the basal canals of the sponge, 

 above the ' wisp.' In this region masses of the annelid about a quarter of an inch 

 in diameter occur, and a multitude of branches pass into the smaller canals adjoin- 

 ing. Two of such masses are especially conspicuous. The intricate manner in 

 which the branches are arranged makes it a very difficult matter to dissect them 

 out, especially when the friability of the annelid and the sharp spicules of the 

 sponge are taken into account. Even after removal from the sponge it is a laborious 

 operation to unravel them without frequent rupture. 



The masses and their numerous branches, as well as the isolated portions, con- 

 sist of a Syllis-like annelid of the thickness of common sewing-thread. No head 

 can be observed either in the parent-stock amongst the masses or in the canals- 

 elsewhere, so that they must either be very few, only occasionally developed, or by 

 some means have been swept off, as it is hard to believe that they are entirely 

 absent. The latter, however, must be the condition in some of the examples (un-- 

 less we are to suppose that all are connected with a single head), which, therefore, 

 would appear to derive nourishment at the open end, yet in many the aperture 

 rapidly develops a bud which nearly closes it. If* in life there are many examples 

 with such open ends, then the whole series branching from them presents an analo- 

 gous condition to that of very elementary animals, the food being swept in with 

 the sea-water to traverse the moniliform nutritive canal throughout the organism. 



The body of the animal stretches, from any of the broken ends, of a nearly 

 uniform diameter for a considerable distance, the numerous narrow segments being 

 distinctly marked, and each furnished laterally with well-formed feet. The latter 

 have dorsally a long and ofteu gracefully curved cirrus, composed of a variable 

 number of segments, since injury and reparation constantly occur; moreover the 

 cirri are alternately long and short. The longer cirri have about twenty-six seg- 

 ments, and all the organs are gently tapered from base to apex. Beneath and- 

 confluent with the base of the cirrus is the somewhat conical setigerous region, 

 which has a few simple bristles, with a stout and slightly curved shaft, the dilated 

 distal portion having the simple terminal process apparently anchylosed to it. 

 This modification of the bristle is peculiar. A single stout spine supports the 

 setigerous region, and, as usual, its point passes to the upper border. The ventral 

 cirrus is broad and short, its tip being within the vertical line of the former division. 



The body of the annelid appears to have a furor for budding — laterally, termin- 

 ally, and wherever a broken surface occurs. The young buds remain slender till 

 they have reached a considerable length, and into each a diverticulum of the ali- 

 mentary canal of the parent enters. These buds, on attaining a certain size, by 



1 See forthcoming Proceedings of the Linnaan Society, ' Zoology,' 



