July 1 8, 1878] 



NATURE 



307 



A New Comet. — By telegram to the Vienna Academy 

 of Sciences, with which body rests the award of the medal 

 for cometary discoveries, it is announced that a telescopic 

 comet was detected on July 7 by Mr. Swift, of Rochester, 

 N.Y. The place at Hh. was in R.A. 265° and N.P.D. 72°, 

 if the telegram is to be read according to the suggestion 

 of the late Prof. Littrow ; the comet was a faint diffused 

 object, and had a slow motion towards the south-west. 



It would be an advantage if arrangements could be 

 made for the communication of telegraphic notices of 

 these discoveries to the Royal Astronomical Society, 

 which is the proper centre for such information in this 

 country. 



Minor Planets. — On June 26 Prof. Peters detected 

 No. 188 in R.A. I5h. 37m., N.P.D. 106° 18', shining as a 

 star of the twelfth magnitude. No. 173, discovered by 

 Borrelly on August 2, 1877, has been named /«^, and No. 

 180, which was found by Cottenot on February 2, 1878, it 

 is proposed to call Eucharis. 



Saturn's Satellites. — Mr. Marth has again pre- 

 pared, evidently at great trouble, ephemerides of the five 

 inner satellites of Saturn, which will be found in Nos. 

 2,205-6 of the Astronomische Nachrichten, as far as 

 October 23, the conclusion to follow. With such elabo- 

 rate prediction, the regular observation of these faint 

 objects should lae assured ; indeed Mr. Marth' s exertions 

 in this direction have already led to excellent results. 



BIOLOGICAL NOTES 



The Male of Salpa.— The development of the 

 spermatozoa in the Salpas has hitherto not been satis- 

 factorily studied. Only two years ago Mr. Brooks, of 

 Boston, stated that the testis developed from the elaso- 

 blast, and moreover maintained that of the two genera- 

 tions which alternate in these pelagic Tunicates — the one 

 set, the "chain" Salpse, are exclusively males, whilst the 

 other set, the "solitary" Salpas, are exclusively females. 

 This view involved the theoretical assumption that the 

 single Qgg which is found in every individual of a chain 

 of Salpse does not really belong to that individual which 

 is only a male, and has the Qgg laid into it by the solitary 

 Salpa from which the chain is derived by budding. 

 Accordingly, the elaeoblast in the solitary Salpa which, 

 according to Brooks, is female, represents the testis and 

 points to a primitive hermaphroditism ; whilst in the 

 chain Salpae (actual males, according to Brooks), the elaso- 

 blast becomes testis. The more usual view is that the 

 solitary Salpae are not sexually differentiated at all, and 

 that the chain Salpae are hermaphrodites. Prof. Salensky, 

 of Kasan, has recently published {Zeitsch. wiss. Zoologie, 

 1878, Supplement 2) some observations on this matter, 

 having previously given a very careful account of the 

 development of these organisms, and at the same time he 

 enters into a discussion of the relationships of various 

 Tunicata which has much interest. He shows that the 

 eggs found in the chain Salpas cannot be regarded as 

 given off from the solitary mother into the budded chain 

 because there is no specialised ovarian cord or rudiment 

 in the proliferous mother. She differs in this respect 

 from the adult proliferous persons in Pyrosoma — which 

 really, as shown by Huxley and by Kowalewsky, give to 

 their buds a part of their own ovarian rudiment. The 

 solitary Salpa has nothing of the kind to give. Further, 

 Salensky shows that the elaeoblast has nothing to do with 

 tbe testis. It exists in the solitary Salpa, and in the 

 chain Salpa appears only for a brief period, and then 

 disappears ; but is certainly not developed into a testis. 

 Accordingly the solitary Salpa is devoid of all trace of 

 either ovary or testis. The elaeoblast appears very 

 probably, according to Salensky, to represent the noto- 

 chord. The tailed larvae of the true Ascidians possess a 

 well-developed notochord, and present to us the ancestral 

 form of the Tunicata, which only persists to the adult 



condition in the Appendicularias. In the Ascidias the tail 

 and notochord atrophy as development advances. In 

 Doliolum the young form which develops from the &^'g 

 has a short tail with an axis apparently intermediate 

 in character between the notochord of the Ascidian 

 tadpole and the elaeoblast of the Salpas. The sexual 

 form of Doliolum developed by budding from a second 

 sexless generation, is devoid of tail. Salensky holds that 

 we must distinguish in the Tunicata such simple budding 

 from the adult as is presented in the Pyrosoma colonies 

 and others, and that kind of budding which definitely 

 characterises the alternation of generations morphologi- 

 cally distinguishable from one another. The sexless 

 nurse, constituting the one generation, appears to retain 

 the characteristics of the ancestral Tunicate form with 

 tail and notochord. It corresponds to the Ascidian tad- 

 pole, and is represented in more or less completely modi- 

 fied condition by the tailed sexless nurses of Doliolum, 

 by the solitary Salpae, and by the Cyathozooid or primary 

 person of the Pyrosoma colony, which gives rise to the 

 colony by a process of budding which it is necessary to 

 distinguish very widely from that which the persons of 

 the colony exhibit at a later stage themselves. Just as 

 the Ascidian tadpole becomes itself atrophied and meta- 

 morphosed so as to form the sexually mature Ascidian, 

 so do the "nurses " above mentioned give rise by budding 

 to a generation not possessing their own archaic characters, 

 but bearing sexual organs and corresponding to the 

 adult Ascidian, and thus we have an alternation of form 

 in the successive gamic and agamic generations. Should 

 multiplication by budding or fission be confined to the 

 later sexual phase, then there is no morphological alterna- 

 tion of generations. Salensky thinks that a hopeful way of 

 gaining a deeper insight into the phenomenon of true 

 metagenesis lies in the further study of the cases pre- 

 sented by Tunicata. E, R. L. 



The Structure and Development of Sponges.— 

 The sponges are at present attracting a very large amount 

 of attention from zoologists and are undergoing investi- 

 gation in the fresh condition, so that their living soft tissues 

 are subjected to the refined methods of modern histology. 

 Prof. Franz Eilhard Schulze, of Gratz, is foremost in this 

 study, the way in which was led by Ernst Haeckel in his 

 monograph of the Calcispongiae. Dr. Keller, of Ziirich, who 

 has previously published on the development of certain 

 calcareous sponges, has now {Zeitsch. wiss. Zoologie, 1878, 

 part 4) given attention to Reniera setnitubulosa, O. Schm., 

 a representative of the commoner marine fibrous sponges. 

 Schulze, by the use of silver nitrate, discovered a dif- 

 ferentiated epithelial covering to the body surface, which 

 was previously denied by Keller, who now admits Schulze's 

 observation to be correct, and adds a similar observation 

 of his own on Reniera. Keller describes the syncytium of 

 Reniera, denies the existence of muscular cells, and 

 recognises certain ''nutritive wander-cells " in the body- 

 wall of the sponge. His observations on "starch-con- 

 taining cells " are of special importance. He was led to 

 attach a high functional importance to the nutritive 

 wander-cells which pass inwards from the flagellate endo- 

 derm-cells, carrying with them assimilated matter neces- 

 sary for the nutrition of the syncytium, which forms a 

 thick wall beyond. His conception of their importance 

 was confirmed by the discovery that many of them contain 

 starch. Keller has made an extensive search for starch in 

 the cell-elements of sponges, and has found it, or rather 

 we should say has obtained the blue reaction with iodine, 

 in cells from the following sponges : — (i) Spongilla 

 lacustris, (2) Reniera liioralis, nov. spec, (3) Myxilla 

 fasciculata, (4) Geodia gigas, (5) Tethya lyncurium, (6) 

 Buberites massa, (7) Suberites flavus. The substance, 

 whatever it may be, which gives the blue reaction, '■» not 

 in a granular condition, but fluid, and in those cells in 

 which it occurs occupies a large vacuole comparable to a 

 fat vacuole. Neither ordinary nor absolute alcohol, nor 



