Io6 



NATURE 



\May 29, 1879 



BIOLOGICAL NOTES 



Museum Pests in Entomological Collections. 

 — Every record of successful contests with destroying 

 agencies in museums will be of interest to collectors, and 

 useful hints as well as valuable data in natural history 

 may be derived from accounts of the animal species 

 which appear in museums in widely separated localities. 

 Very little information is as yet in print concerning 

 museum pests in America, and Dr. H. A. Hagen has 

 rendered a service to science by relating his experiences 

 in the entomological collection of the Museum of Com- 

 parative Zoology, Cambridge, U.S. {Proc. Boston Soc. 

 Nat. Hist., 1878, p. 56). He found Dermestes lardarius 

 very abundant at first, but as it was easily recognisable it 

 was soon extirpated. The excrements of the larva are 

 large, granulous, and jet black. A much more dangerous 

 foe is the larva of Attagenus tnee^aioma (family Dermes- 

 ddae), having small globular ochreous excrements. Dr. 

 Hagen was always able to find the crack in the box, 

 through which the very thin and slender young larva 

 entered. Anthrenus (same family) is represented by three 

 species, of which the commonest in Europe {A. museonitri) 

 is very rare in Cambridge. A. varius, rare in Europe, 

 is the most common pest in the collection, especially in 

 new additions. A. scrophularice,K\i& "carpet bug," has 

 only been known to Dr. Hagen since 1872 in New 

 England, and later still as a museum pest. It has since 

 become very abundant and dangerous. The excrements 

 consist of very fine light brown globules. Ptinus fur, so 

 common in Europe, very seldom attacks the insects at 

 Cambridge. Triboliujii ferrugineuin was imported from 

 the East Indies. The flat body of the larva, as well as 

 of the beetle, made it particularly fit to enter boxes 

 through the smallest crack. It was got under by the aid 

 of tobacco-smoke. The common clothes-moth was found 

 very dangerous, and taught Dr. Hagen the lesson of 

 placing every spreading-board at once in a tightly-closing 

 box. Several years ago Dr. Hagen inclosed some 

 clothes-moths with rotten insects in a glass-stoppered 

 bottle, where they propagated year after year. In the 

 fourth year the moths were noticed to be visibly smaller, 

 and in the sixth most of them were scarcely half the 

 ordinary size. But among them were always one or two 

 of the normal stature. Nothing had been added to their 

 food in these years. Two injurious species of Psocus, 

 which are much attracted by paste and glue, do not 

 infest Dr. Hagen's boxes, which are not lined with paper. 

 Further, every spreading-board is carefully cleaned, and 

 the cracks washed with alcohol before use. Acari have 

 been easily kept out. Dr. Hagen strongly urges the 

 entire separation of entomological rooms from those 

 containing other preserved animals, especially mammals, 

 birds, and skeletons. Having well-closing boxes, and 

 never putting anything into the collection before it is 

 safe, are the only satisfactory precautions. All other 

 recommendations are but a poor substitute for bad boxes. 



Effect of Light on Pelomyxa.— In a very low, 

 amceba-like organism, Pelomyxa -palttstris, Herr Engel- 

 mann recently observed a remarkable action from sudden 

 incidence of a moderate light (Pfliiger' s Archiv fiir Physio- 

 logie, Bd. xix. p. i). Watched in the microscope this 

 organism showed very slow movements, which, however, 

 on shading the object, became much more lively. When 

 the hand was removed, the granular mass in the interior 

 became still, and the body contracted into a ball, as after 

 an electric shock; this effect occurred within a few seconds. 

 With continued moderate light, weak changes of form 

 appeared again, with hardly perceptible locomotion. This 

 experiment was several times repeated with equal success, 

 and the results were especially notable in a djtfk room, 

 into which diffuse daylight could be admitted. When, 

 however, the room was illuminated, not suddenly, but 

 gradually, the pelomyxa showed no effect. 



The Ovule.— One of the most important of the recent 

 contributions to the embryology of plants is, without 

 question. Prof. Warming's memoir, " De 1' Ovule " (.<4«- 

 nales des Scien. Nat. six" sdr., Bot., tome v.). Com- 

 mencing with a sketch of the views as to the origin of the 

 ovule and nucleus, held in 1844 by Ad. Brongniart, which 

 is in brief, "that there are two different origins for the 

 ovule, the one to be found in the immense majority of 

 flowering plants, in which the ovules make their appear- 

 ance on the edges of the carpellary leaves, and represent the 

 lobes or dentations of these leaves, the other confined to 

 a very small number of plants (Primulaceffi, Myrsinaceae, 

 Theophrasteas, and probably the Santalacece), in which the 

 ovules correspond to so many distinct leaves carried on 

 the prolongation of the floral axis. The nucleus is a pro- 

 duction dc novo, a cellular mamelon developed on the 

 upper face of the lobe of the leaf and in the bottom of the 

 cavity where it is formed." Cramer admits and confirms 

 this view. Van Tieghem and Celakovsky also agree to it, 

 with this difference, that to them all the ovules appear as 

 lobes of leaves, and that there are no independent ovular 

 leaves. Warming, too, admits the theory. In every ovule 

 there are, however, two parts essentially different, the funi- 

 culus and the teguments, which are, without doubt, of the 

 nature of leaves, and the nucleus, which is a " new " crea- 

 tion—a veritable "sporangium," as Prantl says, a 

 "sorus" composed of a single sporangium. Discarding 

 for a moment the question whether ovular leaves exist or 

 not (for example, in the yew). Warming doubts whether 

 the funiculus should always be considered as foliar in 

 certain cases. It is, perhaps, only a metablastome 

 sprung from a leaf, but what is essential is that it is never 

 a bud. In the memoir Warming looks at the question 

 steadily from the point of view of histogenesis. The 

 memoir consists of three chapters. On the early deve- 

 lopment of the leaf or ovular mamelon ; on the genesis of 

 the nucleus ; and on the formation of the integuments of 

 the mamelon. These chapters present a most masterly 

 review of the whole question, one in which every due 

 credit is given to the past and present workers in this 

 field of research, and to none more than to the ingenious 

 Slav botanist, Ladislao Celakovsky. It is somewhat 

 difficult to epitomise the author's conclusions, but he 

 recognises that the morphological significance of an 

 organ does not absolutely depend on its position. He 

 demonstrates that the theory of Brongniart is the true and 

 solely admissible one, and he reasons very conclusively 

 against the views of Bronn, Eichler, and Strasburger, who 

 would regard the ovule as a bud, while, in reality, as he 

 says, " the ovule is the homologue of a sporangium." 



Muscles of Crayfish. — While many observations 

 of muscular contraction in vertebrate animals (espe- 

 cially the frog) are on record, the muscles of in- 

 vertebrate animals have been little studied. M. Richet 

 has recently directed his attention to these latter. 

 From experiments with the myograph on the muscles 

 of crayfish, he finds that the contraction of the muscle 

 of a claw lasts nearly ten times as long as that of the 

 caudal muscle (80 to 100 stimulations per second were 

 needed to cause tetanus in the tail, while 2 to 4 sufficed 

 for the claw). The contraction was not more retarded in 

 one muscle than the other ; with strong direct excitations, 

 it is about a hundredth of a second ; with weak it may be 

 four or five hundredths. With the former stimulations 

 apphed to the ganglionic chain instead of directly, the 

 total retardation is about 2 "5 hundredths of a second. 

 The muscle of the tail is very quickly exhausted, and this 

 agrees with the fact that crayfish cannot swim any great 

 distances. On the other hand, the muscle of a claw, 

 stimulated by very closely following electric currents, is 

 not exhausted. While the tetanus of the caudal muscle 

 does not last more than twenty to thirty seconds, the 

 muscle of the claw remains contracted nearly half an 

 hour, and during the first five minutes the constriction ot 



