812 



SCIENCE. 



[N. S. Vol. XXIV. No. 625. 



the very latest morphological methods, a 

 skilled embryologist, and a man of broad cul- 

 ture, in 1897 began to study the development 

 of Encyrtus fvscicollis, a parasite of several 

 species of the genus Hyponomeuta,; publish- 

 ing his preliminary announcement of his first 

 discovery in the same year, indicating that 

 from a single egg of the parasite there de- 

 velop many true embryos. His announced 

 results were received with the greatest interest 

 in France, as evidenced by the appreciative 

 remarks of Giard in his own article just cited. 



With an admirable skill, with extreme 

 powers of observation, and with an indomi- 

 table perseverance, Marchal continued these 

 investigations during six or seven years, pub- 

 lishing four important papers, and finally, in 

 1904, his startling work entitled ' Eecherches 

 sur la Biologie et le Developpement des 

 Hymenopteres Parasites ' — La Polyembryonie 

 Specifique ou Germinogonie, Arch. Zool. Exp. 

 (4), Vol. II., pp. 257-335, pi. IX.-XIII. 



The facts upon which he throws light may 

 be summed up as follows, and in this summary 

 the writer follows Bugnion: 



1. The Encyrtus [Litomastix or Copido- 

 soma] has, as well as its host the Hypono- 

 meuta, a single annual generation. 



2. The oviposition of the Encyrtus takes 

 place after that of the Hyponomeuta, in July 

 or in August, according to the species para- 

 sitized, and it is in the egg of the moth that 

 the parasite introduces its own egg. 



3. Each chain of embryos comes from a 

 single egg, following the division of the germ 

 into several distinct individuals in the morula 

 phase. 



4. A Hyponomeuta egg receives ordinarily 

 only one Encyrtus egg. While it is possible 

 that the Hyponomeuta egg may be pierced 

 two or three times (perhaps by different indi- 

 viduals), in each case it forms in the cater- 

 pillar a corresponding number of chains of 

 embryos. 



5. The nutritive mass in which the embryos 

 are encased results from the proliferation of 

 the amniotic cells furnished by the germ of 

 the Encyrtus (derived from the paranucleus). 



6. The anhiste membrane, as well as the 

 epithelial-like cellules which clothe the in- 



terior, are formed at the expense of mesen- 

 chymatal elements furnished by the organism 

 of the host. These formations can be assim- 

 ilated to an adventitious cyst destined to iso- 

 late the parasites. 



It is upon the eggs of Hyponomeuta malin- 

 ella that the act of oviposition of the Encyr- 

 tus was for the first time observed (1897). 



Marchal having enclosed a branch of apple 

 in a covering of gauze, placed some cocoons 

 of the moth within. The adult insects 

 emerged during the latter part of June and 

 the early part of July. On the fourth several 

 pairs copulated. On the sixth several freshly 

 deposited egg masses were seen on the branch- 

 es. On the eighteenth, a large number of 

 Encyrtus having issued from parasitized cater- 

 pillars placed in the cage, Marchal noticed at 

 half past one in the afternoon (at the time 

 when the rays of the sun were warmest) an 

 Encyrtus which, poised upon an egg batch of 

 the Hyponomeuta, seemed to be about ovi- 

 positing. Profiting by such a favorable op- 

 portunity, he was able, during the four suc- 

 ceeding hours, to follow with a lens the minute 

 parasite which passed from one egg batch to 

 another, piercing the eggs with its ovipositor. 

 The operation lasted each time a little more 

 than half a minute (two minutes toward the 

 end of the day). 



Other observations were carried on upon 

 the parasites of H. mahalehdella. As this 

 insect issues later than the others, Marchal 

 was able, thanks to this fact, to obtain new 

 layings of the Encyrtus through a period ex- 

 tending from the twelfth to the twenty-second 

 of August, and to complete at the same time 

 the material which he needed for his work. 

 He concludes from his latest observations that 

 the Encyrtus does not live more than a dozen 

 days in the imago state. 



The search for the egg of the Encyrtus in 

 the egg of the Hyponomeuta being extremely 

 difficult if one is obliged to dissociate the 

 vitellus, Marchal used the method of cross- 

 section. Having collected on the tenth of 

 September, 1901, the parasitized egg masses 

 of H. mahalehdella; having fixed them in Gil- 

 son's liquid, colored with carmine and having 

 cut them into fine sections, he succeeded in 



