March 1, 18C8.] 



HARDWICKE'S SCIENCE-GOSSIP. 



G3 



observations of Quatrefages and Agassiz, and others 

 have enabled us to understand its true import in 

 many cases. The newly-formed individuals origi- 

 nated by the fission of the posterior rings, are in 

 fact Sexual zooicls. Just as iu the tapeworms the 

 numerous segments, which when ripe become 

 detached and maintain a separate vitality, are 

 Sexual zooids, destined to carry and disseminate 

 the ova, so in Syllis prolifica, a species frequent 

 on our coasts, "the anterior half — now an entire 

 worm— continues to eat as before, and conduct 

 itself as any independent annelid ; but the individual 

 formed by the posterior half is destined solely to 

 the generation of its species. It does not eat ; and 

 its intestinal canal having become unnecessary, 

 wastes and is atrophied. As, however, this part 

 contained the whole generative organs of the primary 

 individual, the life of it is prolonged by self-nutri- 

 tion, long enough to permit the maturation of the 

 numerous ova, and by their dispersion, and evolution 

 afterwards, the race is continued and multiplied." 

 The posterior segment or " tail " of course perishes, 

 at the same time with the rings which were de- 

 tached with it, and in truth its life is shorter than 

 that of the anterior segment, which is the true 

 representative of the species, and which may form 

 a new tail, and in time undergo new fission, and 

 develop new sexual buds. It is doubtful whether 

 the phenomenon of fission in the fresh- water species, 

 Nais, Stylaria, &c, has the same significance. I 

 have frequently watched the process in Stylaria 

 [Nais proboscidea, Mull.), and Nais serpentina, but 

 could never satisfy myself that the new-formed 

 segments differed in any respect from the anterior 

 moiety. It is quite possible that I may be mistaken, 

 but it seemed to me that in neither the old or new 

 parts of individuals undergoing fission were ova or 

 spermatozoa present. Perhaps the true sexual re- 

 production of these worms may be limited to certain 

 seasons of the year; and in the meantime, as is 

 observed in many of the lower animals and plants, 

 the species is capable of indefinite extension by a 

 sexual fission, or budding. Certainly, the tail 

 segment, in these species, can claim no special im- 

 munity from death. The section generally takes 

 place near the centre of the body, the head portion 

 forming a new tail, and the tail portion a new head, 

 with its eyes, mouth, and cerebral ganglia— truly 

 a circumstance wonderful enough without endowing 

 it with immortality ! In a few days it is impossible 

 to say which individual was derived from the head, 

 which from the tail ; and very likely we shall find 

 both of them undergoing new segmentation, or, 

 quite as likely, both may have perished ! " There 

 is nothing new under the sun,"— and the prelections 

 of your correspondent remind us of the ancient 

 belief that, the os sacrum was indestructible, and 

 from it, as from a seed, the new body at the re- 

 surrection should originate.— B. C. 



ZOOLOGY. 



A Daring Hawk.— Old Powell, at Harrow 

 Weald, was at work in his garden yesterday (June 7, 

 1S63), when a sparrow dashed up against him, 

 closely pursued by a sparrow-hawk. The hawk, 

 nothing daunted by his presence, seized the sparrow, 

 which had fallen at Powell's feet, and bore it 

 screaming away. — liar ting's Birds of Middlesex. , 



Wasp and Spider. — The recent discussion in 

 your columns about the poison in the fangs of 

 spiders may be taken to have set the question at 

 rest. It explains a thing which has often puzzled 

 me, the fact that spiders can hold their own in 

 battle against such terrible adversaries as wasps. 

 I have frequently put a spider and a wasp together 

 under a glass, and forced them to fight. I thought 

 it no cruelty, as they are Arcades ambo, both strong 

 men, and perfectly well able to take care of them- 

 selves. When left alone under the glass they 

 generally avoided one another, until irritated by 

 being pushed together. When this was done, a 

 terrific battle ensued, generally ending in the death 

 of one of the combatants. When the spider was of 

 the smaller species, the wasp always conquered, and 

 on one occasion I saw a wasp bite the spider in two 

 at the narrow part. But when the spider was of 

 the medium size, I have seen him, just as often as 

 not, kill the wasp ; a result which surprised me ex- 

 tremely, not knowing at the time that he also was 

 armed with poisonous weapons. I never pitted a 

 wasp against the large garden spider, but I believe 

 against him he would not have even " a chance." 

 At least, a friend to whom I was speaking of it 

 the other day, told me he saw a wasp drop off 

 a ripe pear, on the ground, and instantly, before 

 he had righted, a large garden spider pounced 

 upon him and carried him into his den. Other 

 spiders, however, consider sometimes that dis- 

 cretion is quite as good as valour where wasps 

 are concerned. On this point I think books of 

 natural history have not quite correct information. 

 I have read more than once in books that spiders 

 when a wasp is caught in their webs, knowing 

 they have caught a tartar, immediately break away 

 the web themselves to let him loose, in fear of his 

 destroying it altogether in his struggles. This 

 may sometimes, but certainly it does not always 

 happen. Late in this present autumn, when out 

 naturalising, my attention was attracted by the web 

 of a geometrical spider, in the centre of which the 

 owner was at work upon what seemed to be a round 

 ball of spider-silk. On going up to examine it 

 closely, I found it was a live wasp caught in the 

 web, which the spider was tying up in the most 

 artistic style, preparatory of course to regaling him- 

 self upon his corporeal juice. Keeping himself out 

 of harm's way, he wound coil after coil round him, 



