524 



NATURE 



[Oct. 24, 1872 



have received, tliroiigh tlie kindness o( Dr. Dohrn, a copy of 

 the Sitzunijsberichte of the Municli Academy of Novembev 4, 

 1S71, in which they are fully given. It appears that though an 

 occasional female appeared among tlie male broods produced 

 by unfertilised females, this was, in every case where it happened, 

 fully accounted for by the accidental access of a fertilised female, 

 or some such misadventure, duly noted in the records kept of the 

 observations. 



Of tlie fourth and fifth chapters, treating of Partheno- 

 genesis in the Lepidoptera, Psyche Helix, Solcnobia tr'iqnc- 

 Irdla and Uchendla, we have not space to speak in detail. 

 Tlie same intimate inquiry, and the same very necessary 

 prodigality in the amount of material subjected to ex- 

 periment, which we noted above as to Polistes, charac- 

 terise Prof. Siebold's treatment of these cases. The parthe- 

 nogenesis in these cases produces female broods, and though 

 the male of Psvilie Ildix has been discovered since Siebold's 

 former researches on this moth, his conclusion is by no means 

 invalidated, for the males are excessively rare. They were 

 first discovered by Claus, of Marburg, who has indicated 

 cliaracters by which future observers may distinguish the 

 sex of the caterpillars. Out of many hundreds of broods reared 

 l)y Siebold, taken in various places, ranging from the Baltic to 

 the plains of Lombardy, only once did he obtain males. There 

 appear to be thus broods which are entirely female, and broods 

 which are of mixed sexes. The conditions under which tlie 

 male sex makes its appearance are not yet ascertained. It is ex- 

 ceedingly desirable tliat those who may be fortunate enough to 

 come across a mixed brood, should make experiments to as- 

 certain if all the eggs which are fertilised produce males. The 

 females of the purely female broods are completely developed in 

 every respect, having perfect copulatory organs, and the egg is 

 furnished with a micropyle ; therefore, as Siebold maintain;, 

 they must not be called pseud-ova. It should be menlioned 

 that the inquiries necessary to establish the identity of the 

 species, and the distinctive characters with regard to these 

 little moths, have occupied a great deal of our autlior's time 

 and attention, and are here recorded. In regaid both to 

 Psyche and Solenobia examination with the microscope was 

 employed to determine the absence of male elements from the 

 iLLtptacnhtni scrninis ; and we have moreover an account of 

 tlie structure of the ovaries. In relation to this matter, Professor 

 Siebold takes the opportunity of replying to some criticisms of 

 his former work by M. Plateau, who appears to have made little 

 of the arguments based on the proof thus obtained of virginity, 

 without knowing the real extent and nature of Siebold's studies, 

 having, in fact, only read of them in an imperfect abstract. It 

 appears also that M. Plateau took "eineinziger Fundort" to mean 

 "un naturaliste coUecteur," an amusing mistake to which our 

 attention is drawn in a note, p. 155. We may briefly mention 

 here with regard to Solenobia, that it appears that S. Uchciidla 

 is only the female brood of S. piiidi, of which males and females 

 regularly occur. No structural difference appears to exist between 

 tlie two kinds of females, but the former, on escaping from the 

 chrysalis-sac, at once proceed to lay eggs, which produce invari- 

 ably females ; whilst the latter wait for copulation, and if that be 

 withheld, die, and dry up without laying their eggs. These insects 

 offer most promising material for further researches on the condi- 

 tions attending the dift'erentiation of sex. 



We now come to the sixth and last chapter, on " the Partheno- 

 genetic Reproduction in Apus and allied Cnistacea." Already, 

 in 1S56, Siebold had stated his supposition that Apiis caiuri- 

 formis, Limuadia gigeis, and Polypheniits ocitliis, in which species 

 no males had been observed, presented examples of true partheno- 

 genesis, and were not to be regarded as bud-producing "nurses," 

 in a so-called alternation of generations. Leuckart subsequently 

 expressed the same opinion with regard to the reproduction, in- 

 dependent of males, observed in Daplinia, Apus, and LiiiDiaiUii. 

 Ever since that period Siebold has continually kept an eye 

 upon Apus. In 185S the males of Apus were discovered by 

 Kozubowski, and Siebold received specimens from various 

 localities, lie thus learned to distinguish with perfect facility 

 the two sexes, and was enabled now to convince himself that, as 

 with the Lepidoptera above spoken of, so with Apus, broods 

 occur which are entirely destitute of males, and go on repro- 

 ducing parthenogenetically, whilst other broods occur in which 

 both sexes are present. The number of Ajjus of two species — 

 Apus cancrifonnis and Apus proJuclns — examined by Siebold, 

 amounts actually to some thousands. He received quantities 

 taken from various ponds in middle Europe (Apus occurs in 



shallow pools which dry up during parts of the year, and it can 

 be taken in immense quantity), and had the opportunity of 

 studying one p^nd — that at Gossberg, near Munich, with 

 minuteness, from the year 1864 to the year 1869 inclusive, 

 besides casual examinations of the same pond in 1 85 7 and 1S58. 

 Time after time, taking several hundreds of the Apus from the 

 pond, he never found a single male amongst them. On one occa- 

 sion he had the whole contents of the little pond removed 

 vrith the greatest care, so as to feel sure that he had obtained 

 every Apus present. He received on this occasion 5,796 speci- 

 mens of Apus, rocry one of lohich lieing carefully csaiiihietl 

 proved to be female. At the same time 2,576 specimens of 

 Branchipus were obtained from the pond, which were, as usual, 

 of both sexes. In those cases where ponds afforded both males 

 and females of Apus, it is remarkable that the proportion of 

 the sexes was very variable. The highest proportion of males 

 appears to be in a case recorded by Sir John Lubbock, who found 

 thirty-three male and thirty-nine female Apus pi-oditctus in a pond 

 near Rouen, wliilst among 193 specimens of .Ipiis cancrifonnis, 

 from a locality near Krakow, only one male occurred. What is 

 most important about this variation in the proportion of males to 

 females is that in two or three localities, furnishing mixed 

 generations of Apus, from which he has received, year after year, 

 numbers of specimens, Siebold has observed an apparent con- 

 stantly-augmenting disproportion of males to females, and he 

 is led to tlie supposition that in these cases the males 

 will at last cease altogether, and thus a female generation be 

 produced which will continue to reproduce itself partheno- 

 genetically, as in the Gossberg and a gieat number of other ponds. 

 This is, however, by no means proved ; and we have no idea at 

 present as to how the males may make their appearance again, 

 or what are the conditions affecting their development and extinc- 

 tion. It occurred to .Siebold that an objection might be urged 

 against parthenogenesis in Apus, in that, although he examined 

 consecutive generations and found them always female, he could 

 not be sure tliat males had not been present before he took his 

 specimens, and had not died and decomposed after having 

 fertilised the females. To meet such an objection, he firstly 

 made himself tlinroughly acquainted with the ma'e generative 

 organs and the spermatozo.!, and secondly with the ovaries arid 

 their development. He found the spermatozoa to be motionless 

 like those of other Crustacea, and he never succeeded in detecting 

 any of them in the female genitalia amongst the specimens 

 belonging to supposed female generations. But he equally 

 failed to find spermatozoa or a receptacle for them in the female 

 genitalia of the specimens of mixed generations, and therefore 

 no conclusion could be drawn from the observation. Tlie 

 structure and development of the ovum, however, made this 

 observation decisive, since it was found that an egg-shell forms 

 round the ovum in the uterus, and, in the absence of a 

 micropyle, fertilisation, if it takes place at all, must be accom- 

 plished before this shell is hardened. A further proof of 

 another kind Mas obtained by experiment. Having removed 

 eggs from females, which certainly at the time contained no 

 spermatozoa, Siel^old placed them in a small tank, and from 

 these obtained Apus-embryos. Others were reared to maturity 

 from eggs taken in the pond. 



The relative size of male and female is a question about which 

 there is some interest ; difterences which have been observed 

 seem to depend on this, that Apus continues growing as long as 

 the pond in which it lives does not dry up, and hence the eggs 

 which hatch soonest give the largest-sized progeny. In his tabular 

 statements Siebold gives measurements of the specimens ex- 

 amined by him at dilTerent times from various localities. 



A few words must be said here upon the very extraordinary 

 history of the ovum of Apus made out by Siebold, the structures 

 being identical, whether the female examined belonged to a 

 parthenogenetic or digenetic brood. The essential female organs 

 of reproduction in Apus may be roughly described as two large 

 tubes placed on either side the alimentary canal, opening exter- 

 nally at the posterior end, and giving off towards the other end 

 primary and secondary branches. On the ends of these short 

 secondary branches are situated the egg follicles. Four cells appear 

 in each egg follicle in a very early stage of its development, and one 

 of these takesonmorerapidgrowth — becomingtheegg-cell — whilst 

 the others disappear as deutoplasmogen or vitellogenous cells ; 

 the egg then acquires some size and a red colour, and has a visible 

 germinal vesicle. But such eggs are mucli smaller than the eggs 

 obsei-vable in the main stem of the ovarian tube, and this appears 

 to be the very startling explanation. The eggs escape from their 



