420 



NATURE 



\Augttst 29, 1889 



The author contends that " we are brought squarely to 

 the conclusion that the foetal placenta is chorionic," and 

 that "from this premise pbylogenetic speculation must 

 start." He tells us that, '"'so far as our present knowledge 

 enables us to judge, the discoidal is probably the primi- 

 tive placental type." With this we heartily agree, and it 

 has always appeared to the writer of the present article 

 that the same conclusion is, on the Balfourian hypothesis 

 {from which Prof Minot dissents) that both the yolk-sac 

 and allantois were primitively concerned in rendering the 

 chorion vascular, by far the most natural one warranted by 

 the facts. The belief in the primitive nature of the diffuse 

 placenta is, beyond doubt, largely attributable to its non- 

 deciduous character. With Dr. Minot, we are opposed 

 to Ryder's theory of the " origin of the discoidal placenta 

 by constriction of the villous area of the zonary placenta." 

 We would rather reverse the order, and regard the zonary 

 type as transitional between the more primitive discoidal 

 one and the more recent and modified diffuse cotyle- 

 donary and metadiscoidal varieties, regarding the re- 

 placement of the discoidal in the zonary type as primarily 

 due to extension consequent upon the complete with- 

 drawal of the yolk-sac from the chorion. Under this 

 hypothesis the simple nature of the villi of the diffuse 

 placenta night well be considered secondary. 



Dr. Minoi's paper furnishes a moral which cannot be 

 too often borne in mind, viz. that it is not necessary to 

 look beyond the most familiar organisms for material for 

 legitimate work: nei her a " new body " nor " a hitherto 

 undescribed organism " are indispensable to the building 

 up of a reputation. 



Mr. Allis's paper is one for which we have eagerly 

 watched, it being (as our readers will be aware) the first 

 of a promised series. The author maps and classifies the 

 sense-organs of the head with minute accuracy, at the 

 leading stages of growth. When he tells us that " as 

 many as thirty-seven hundred " pores " were counted on 

 the head of a single large specimen,'' some idea of the 

 laboriousness of his task may be formed ; and on finding 

 that he has worked out the detailed relationships of the 

 parts to the individual bones, that he has, in addition to 

 working out their development, determined the limits of 

 individual variation and taken count of abnormalities, it is 

 clear that his labour is a labour of love. The thorough- 

 ness of his work and the beauty of his illustrations must 

 be seen to be appreciated ; and should he complete his 

 task, maintaining the standard of excellence with which 

 he has started, he will have merited the regard of biologists 

 tor all time. He has brought to light the surprising fact 

 that many of the first formed openings of the cutaneous 

 canal system fuse to form pores, and that the dendritic 

 systems and groups of pores which, in the adult, re- 

 place these, arise to a large extent from their repeated 

 dichotomous division. 



The author deals neither with polemics nor generalities,^ 

 nor does he even allude to striking facts which his figures 

 show, foreign to his immediate inquiry. Consideration of 

 these is doubtless deferred. He deals incidentally with 

 the neuro-epithelium of the spiracular cleft discovered by 

 Wright ; this he regards as a sense-organ, which was 

 " regularly developed in the epidermal covering of the 

 head along with the other organs of the infra-orbital line, 

 but, lying near the edge of the spiracular cleft, it wandered 

 into this cleft as it was closed." Indeed, it is upon this 

 observation that the author's co-editor confessedly bases 

 his belief in the migratory origin of the gustatory organs ; 

 and Mr. Allis's allied discovery that " the nasal pits are 

 inclosed in the same way that the lateral canals are " will 

 be welcomed with especial interest by embryologists of 

 the hour. 



We have often wondered that our American brethren 

 should have been so tardy in working out the structure 



' He appears to have overlooked an important paper by Fritsch, in Sizb. 

 Berlin A/cad., 1888, viii., p. 273. 



and development of their native rarissima. Their 

 Opossum and their Urodeles are now receiving attention, 

 a beginning has been made with Lepidosteus, the Gym- 

 nophiona remain. Zoologists of the Old World could 

 desire nothing better at the hands of their New World 

 co7jfrercs than a series of exhaustive monographs upon 

 the structure and development of the animals named, 

 uniformly with the one now under review. A better 

 model of conscientious work it would be difficult to 

 produce. G. B. H. 



THE AUGUST PERSE IDS OF 1889. 



'T'HE moon being full on the morning of August il, it 

 -*■ was hardly to be expected that the Perseid meteors 

 would exhibit a notable display this year. Apart, how- 

 ever, from the ill effect the moonlight must certainly have 

 exercised upon the visible character of the shower, there 

 is no doubt that the phenomenon has proved one of minor 

 importance. I have never observed, during the previous 

 twenty-two years, so scanty a fall of the August meteors. 



I made observations on July 26, 27, 29, 30, 31, and 

 August 3, for the express purpose of determining the 

 radiants of early Perseids, but failed to secure an adequate 

 number of paths to carry out that intention. In watches 

 extending over eleven hours I counted 89 meteors, but 

 not more than 6 of these could have been Perseids. It 

 was evident that this system was very feebly represented.. 

 Yet in 1887 it formed a very distinct and fairly active 

 display as early as July 19 and 22, and I have sometimes 

 remarked decided traces of it in the second week of 

 July. In 1878 and several other years I observed that 

 the Perseids made a prominent shower towards the close 

 of that month, and it was easy to find the position of its 

 radiant on every clear night. But this has been quite 

 impracticable in 1889, owing to the exceptional scarcity of 

 mteors. 



On August 7, 1889, I looked towards the eastern region 

 of the firmament during the 2| hours from ii^h. to 

 I4h., and recorded 28 meteors only. Amongst these 

 were 10 Perseids with a radiant point very sharply defined 

 at 41^ + 58'. They were rather small and traversed short 

 paths ; nearly all of them appeared near the centre from 

 which they radiated. The shower was, however, of greatly 

 inferior character to what was expected on a date so near 

 the maximum. The ensuing nights were pretty clear, 

 but in the brilliant moonlight meteoric apparitions were 

 very infrequent. On August 10 only 8 Perseids were 

 noticed in one hour before midnight. 



My recent observations would seem to indicate that we 

 have passed through a minimum of the August meteors. 



The Aquarids which are generally very abundant at 

 the end of July were also weakly displayed this year. I 

 registered 6 of them between July 27 and August 3, from 

 a radiant at 336" - 13". Of the other streams which dis- 

 tinguish this epoch I saw several, the principal of them 

 being a shower of Cepheids from 329*^ -f- 62° and of 

 Cassiopeids from 8° + 52°. W. F. Denning. 



NOTES. 

 We print to-day the Report of the Committee appointed by 

 the Treasury on the Scientific Collections at South Kensington 

 under the control of the Science and Art Department. It is 

 some seventeen years since the Duke of Devonshire's Com- 

 mission recommended their formation, and it would seem now 

 that something may really be done after so long a delay. The 

 Committee, it will be seen, di>cu?s both the question of a new 

 building and that of the proper organization of such collections. 

 The eminence of the members of the Committee adds great 

 weight to their recommendations, and the Report has been very 

 favourably received by the Press. 



